Iron-based sintered alloy having excellent machinability

ABSTRACT

This iron-based sintered alloy contains 0.05 to 3% by mass of calcium carbonate or 0.05 to 3% by mass of strontium carbonate. As a result, an iron-based sintered alloy having excellent machinability is obtained.

CROSS-REFERENCE TO PRIOR APPLICATION

This is a U.S. national phase application under 35 U.S.C. §371 ofInternational Patent Application No. PCT/JP2004/003094 filed Mar. 10,2004, and claims the benefit of Japanese Patent Application No.2003-62854 filed Mar. 10, 2003 which is incorporated by referenceherein. The International Application published in Japanese on Sep. 23,2004 as WO 2004/003094 A1 under PCT Article 21(2).

TECHNICAL FIELD

The present invention relates to an iron-based sintered alloy havingexcellent machinability which is used as materials for various machinecomponents.

BACKGROUND ART

With the progress of a sintering technique, various electric componentssuch as yoke and rotor, and various machine components such as pistonsfor shock absorber, rod guides, bearing caps, valve plates forcompressor, hubs, forkshifts, sprockets, toothed wheels, gears andsynchronizer hubs have recently been produced using an iron-basedsintered alloy obtained by sintering a raw powder mixture. For example,it is known that an iron-based sintered alloy having the compositionconsisting of pure iron and 0.1 to 1.5% by mass of P, the balance beingFe and inevitable impurities, is used to produce various electriccomponents such as yokes and rotors. It is known that an iron-basedsintered alloy having the composition consisting of 0.1 to 1.2% by massof C, the balance being Fe and inevitable impurities, is used to producepistons for shock absorber, and lot guides. It is known that aniron-based sintered alloy having the composition consisting of 0.1 to1.2% by mass of C and 10 to 25% by mass of Cu, the balance being Fe andinevitable impurities, is used to produce bearing caps, and valve platesfor compressor. It is known that an iron-based sintered alloy having thecomposition consisting of 0.1 to 1.2% by mass of C and 0.1 to 6% by massof Cu, the balance being Fe and inevitable impurities, is used toproduce forkshifts, sprockets, gears, toothed wheels, and pistons forshock absorber. It is known that an iron-based sintered alloy having thecomposition consisting of 0.1 to 1.2% by mass of C, 0.1 to 6% by mass ofCu, 0.1 to 10% by mass of Ni and 0.1 to 6% by mass of Mo, the balancebeing Fe and inevitable impurities, is used to produce CL cranks,sprockets, gears, and toothed wheels.

It is known that an iron-based sintered alloy having the compositionconsisting of 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, thebalance being Fe and inevitable impurities, an iron-based sintered alloyhaving the composition consisting of 0.1 to 1.2% by mass of C, 0.1 to10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being Fe andinevitable impurities, an iron-based sintered alloy having thecomposition consisting of 0.1 to 1.2% by mass of C, 0.1 to 10% by massof Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balancebeing Fe and inevitable impurities, an iron-based sintered alloy havingthe composition consisting of 0.1 to 1.2% by mass of C, 0.1 to 6% bymass of Cu, 0.1 to 10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1to 6% by mass of Mo, the balance being Fe and inevitable impurities, aniron-based sintered alloy having the composition consisting of 0.1 to1.2% by mass of C and 0.1 to 10% by mass of Ni, the balance being Fe andinevitable impurities, an iron-based sintered alloy having thecomposition consisting of 0.1 to 1.2% by mass of C, 0.1 to 10% by massof Ni and 0.1 to 6% by mass of Mo, the balance being Fe and inevitableimpurities, and an iron-based sintered alloy having the compositionconsisting of 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1to 10% by mass of Ni, the balance being Fe and inevitable impurities,are used as materials of various machine components such as sprockets,gears and toothed wheels.

Also it is known that an iron-based sintered alloy having thecomposition consisting of 1.0 to 3.0% by mass of C, 0.5 to 8% by mass ofCu and 0.1 to 0.8% by mass of P, the balance being Fe and inevitableimpurities, are used as materials of valve guides.

Also it is known that an iron-based sintered alloy having thecomposition consisting of 0.3 to 2.5% by mass of C, 0.5 to 12% by massof Cr, 0.3 to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% bymass of V, the balance being Fe and inevitable impurities, an iron-basedsintered alloy having the composition consisting of 0.3 to 2.5% by massof C, 0.5 to 12% by mass of Cr, 0.3 to 9% by mass of Mo, 3 to 14% bymass of W, 1 to 6% by mass of V and 5 to 14% by mass of Co, the balancebeing Fe and inevitable impurities, an iron-based sintered alloy havingthe composition consisting of 0.3 to 2% by mass of C, 0.5 to 10% by massof Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, and one ormore kinds selected from among 1 to 5% by mass of W, 0.05 to 1% by massof Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, thebalance being Fe and inevitable impurities, an iron-based sintered alloyhaving the composition consisting of 0.3 to 2% by mass of C, 0.5 to 10%by mass of Cr, 0.3 to 16% by mass of Mo and 0.1 to 5% by mass of Ni, oneor more kinds selected from among 1 to 5% by mass of W, 0.05 to 1% bymass of Si, 0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and10 to 20% by mass of Cu, the balance being Fe and inevitable impurities,and an iron-based sintered alloy having the composition consisting of0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to 5% by mass ofNi and 0.1 to 2% by mass of Co, the balance being Fe and inevitableimpurities, are used as materials of valve seats.

Also it is known that an iron-based sintered alloy having thecomposition consisting of 15 to 27% by mass of Cr and 3 to 29% by massof Ni, the balance being Fe and inevitable impurities, an iron-basedsintered alloy having the composition consisting of one or more kindsselected from among 15 to 27% by mass of Cr, 3 to 29% by mass of Ni, 0.5to 7% by mass of Mo and 0.5 to 4% by mass of Cu, the balance being Feand inevitable impurities, an iron-based sintered alloy having thecomposition consisting of 10 to 33% by mass of Cr, the balance being Feand inevitable impurities, an iron-based sintered alloy having thecomposition consisting of 10 to 33% by mass of Cr and 0.5 to 3% by massof Mo, the balance being Fe and inevitable impurities, an iron-basedsintered alloy having the composition consisting of 10 to 33% by mass ofCr and 0.5 to 3% by mass of Mo, the balance being Fe and inevitableimpurities, an iron-based sintered alloy having the compositionconsisting of 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C, thebalance being Fe and inevitable impurities, an iron-based sintered alloyhaving the composition consisting of 14 to 19% by mass of Cr and 2 to 8%by mass of Ni, the balance being Fe and inevitable impurities, and aniron-based sintered alloy having the composition consisting of 14 to 19%by mass of Cr and 2 to 8% by mass of Ni, and one or more kinds selectedfrom among 2 to 6% by mass of Cu, 0.1 to 0.5% by mass of Nb and 0.5 to1.5% by mass of Al, the balance being Fe and inevitable impurities, areused as materials of corrosion-resistant machine components.

Various machine components made of these conventional iron-basedsintered alloys are produced by blending predetermined raw powders,mixing the powders and compacting the powder mixture to obtain a greencompact, and sintering the resulting green compact in a vacuum,dissociated ammonia gas, N₂+5% H₂ gas mixture, endothermic gas orexothermic gas atmosphere, and are finally shipped after piercing therequired position using a drill and cutting or grinding the surface.Machining such as piercing, cutting or grinding is conducted by usingvarious cutting tools. When machine components have a lot of positionsto be cut, cutting tools are drastically worn out, resulting in highcost. Therefore, there has been made a trial of suppressing wear of thecutting tool by a method of adding about 1% of a MnS or MnO powder andsintering the resulting green compact thereby to improve machinabilityof the cutting tool (see Japanese Patent Application, First PublicationNo. Hei 3-267354) or a method of adding a CaO—MgO—SiO₂-based complexoxide, thereby to improve machinability (see Japanese PatentApplication, First Publication No. Hei 8-260113) of the cutting tool,and thus reducing the cost.

DISCLOSURE OF THE INVENTION

An iron-based sintered alloy obtained by adding a conventional MnSpowder, MnO powder or CaO—MgO—SiO₂-based complex oxide powder andsintering the resulting green compact has machinability, which isimproved to some extent, but is not still satisfactory. Therefore, it isrequired to develop an iron-based sintered alloy having more excellentmachinability.

From such a point of view, the present inventors have intensivelystudied so as to obtain an iron-based sintered alloy having moreexcellent machinability, which can be used as materials of variouselectric and machine components. As a result, they have found that aniron-based sintered alloy containing 0.05 to 3% by mass of a calciumcarbonate powder or an iron-based sintered alloy containing 0.05 to 3%by mass of a strontium carbonate powder has more improved machinability.

The present invention has been made based on such a finding and ischaracterized by the followings:

-   (1) an iron-based sintered alloy having excellent machinability,    comprising 0.05 to 3% by mass of calcium carbonate,-   (2) an iron-based sintered alloy having excellent machinability with    the composition consisting of 0.05 to 3% by mass of calcium    carbonate, the balance being Fe and inevitable impurities,-   (3) an iron-based sintered alloy having excellent machinability with    the composition consisting of 0.05 to 3% by mass of calcium    carbonate and 0.1 to 1.5% by mass of P, the balance being Fe and    inevitable impurities,-   (4) an iron-based sintered alloy having excellent machinability with    the composition consisting of 0.05 to 3% by mass of calcium    carbonate and 0.1 to 1.2% by mass of C, the balance being Fe and    inevitable impurities,-   (5) an iron-based sintered alloy having excellent machinability with    the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the    balance being Fe and inevitable impurities,-   (6) an iron-based sintered alloy having excellent machinability with    the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the    balance being Fe and inevitable impurities,-   (7) an iron-based sintered alloy having excellent machinability with    the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to    10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe    and inevitable impurities,-   (8) an iron-based sintered alloy having excellent machinability with    the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the    balance being Fe and inevitable impurities,-   (9) an iron-based sintered alloy having excellent machinability with    the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and    0.1 to 6% by mass of Mo, the balance being Fe and inevitable    impurities,-   (10) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1    to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being    Fe and inevitable impurities,-   (11) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to    10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of    Mo, the balance being Fe and inevitable impurities,-   (12) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni,    the balance being Fe and inevitable impurities,-   (13) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and    0.1 to 6% by mass of Mo, the balance being Fe and inevitable    impurities,-   (14) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1    to 10% by mass of Ni, the balance being Fe and inevitable    impurities,-   (15) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1    to 0.8% by mass of P, the balance being Fe and inevitable    impurities,-   (16) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3    to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V,    the balance being Fe and inevitable impurities,-   (17) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3    to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and    5 to 14% by mass of Co, the balance being Fe and inevitable    impurities,-   (18) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to    16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds    selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si,    0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance    being Fe and inevitable impurities,-   (19) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to    16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds    selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si,    0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20%    by mass of Cu, the balance being Fe and inevitable impurities,-   (20) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to    5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe    and inevitable impurities,-   (21) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the    balance being Fe and inevitable impurities,-   (22) an iron-based sintered alloy having excellent machinability    with the composition consisting of one or more kinds selected from    among 0.05 to 3% by mass of calcium carbonate, 15 to 27% by mass of    Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4% by    mass of Cu, the balance being Fe and inevitable impurities,-   (23) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate and 10 to 33% by mass of Cr, the balance being Fe and    inevitable impurities,-   (24) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the    balance being Fe and inevitable impurities,-   (25) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C,    the balance being Fe and inevitable impurities,-   (26) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the    balance being Fe and inevitable impurities,-   (27) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of calcium    carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and    one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to    0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being    Fe and inevitable impurities,-   (28) an iron-based sintered alloy having excellent machinability,    comprising 0.05 to 3% by mass of strontium carbonate,-   (29) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, the balance being Fe and inevitable impurities,-   (30) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate and 0.1 to 1.5% by mass of P, the balance being Fe and    inevitable impurities,-   (31) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate and 0.1 to 1.2% by mass of C, the balance being Fe and    inevitable impurities,-   (32) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C and 10 to 25% by mass of Cu, the    balance being Fe and inevitable impurities,-   (33) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Cu, the    balance being Fe and inevitable impurities,-   (34) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to    10% by mass of Ni and 0.1 to 6% by mass of Mo, the balance being Fe    and inevitable impurities,-   (35) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C and 0.1 to 6% by mass of Mo, the    balance being Fe and inevitable impurities,-   (36) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Cr and    0.1 to 6% by mass of Mo, the balance being Fe and inevitable    impurities,-   (37) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni, 0.1    to 10% by mass of Cr and 0.1 to 6% by mass of Mo, the balance being    Fe and inevitable impurities,-   (38) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu, 0.1 to    10% by mass of Ni, 0.1 to 10% by mass of Cr and 0.1 to 6% by mass of    Mo, the balance being Fe and inevitable impurities,-   (39) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C and 0.1 to 10% by mass of Ni,    the balance being Fe and inevitable impurities,-   (40) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 10% by mass of Ni and    0.1 to 6% by mass of Mo, the balance being Fe and inevitable    impurities,-   (41) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.1 to 1.2% by mass of C, 0.1 to 6% by mass of Cu and 0.1    to 10% by mass of Ni, the balance being Fe and inevitable    impurities,-   (42) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 1.0 to 3.0% by mass of C, 0.5 to 8% by mass of Cu and 0.1    to 0.8% by mass of P, the balance being Fe and inevitable    impurities,-   (43) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3    to 9% by mass of Mo, 3 to 14% by mass of W and 1 to 6% by mass of V,    the balance being Fe and inevitable impurities,-   (44) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.3 to 2.5% by mass of C, 0.5 to 12% by mass of Cr, 0.3    to 9% by mass of Mo, 3 to 14% by mass of W, 1 to 6% by mass of V and    5 to 14% by mass of Co, the balance being Fe and inevitable    impurities,-   (45) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to    16% by mass of Mo and 0.1 to 5% by mass of Ni, and one or more kinds    selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si,    0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, the balance    being Fe and inevitable impurities,-   (46) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.3 to 2% by mass of C, 0.5 to 10% by mass of Cr, 0.3 to    16% by mass of Mo and 0.1 to 5% by mass of Ni, one or more kinds    selected from among 1 to 5% by mass of W, 0.05 to 1% by mass of Si,    0.5 to 18% by mass of Co and 0.05 to 2% by mass of Nb, and 10 to 20%    by mass of Cu, the balance being Fe and inevitable impurities,-   (47) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 0.3 to 2% by mass of C, 0.1 to 3% by mass of Mo, 0.05 to    5% by mass of Ni and 0.1 to 2% by mass of Co, the balance being Fe    and inevitable impurities,-   (48) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the    balance being Fe and inevitable impurities,-   (49) an iron-based sintered alloy having excellent machinability    with the composition consisting of one or more kinds selected from    among 0.05 to 3% by mass of strontium carbonate, 15 to 27% by mass    of Cr, 3 to 29% by mass of Ni, 0.5 to 7% by mass of Mo and 0.5 to 4%    by mass of Cu, the balance being Fe and inevitable impurities,-   (50) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate and 10 to 33% by mass of Cr, the balance being Fe and    inevitable impurities,-   (51) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 10 to 33% by mass of Cr and 0.5 to 3% by mass of Mo, the    balance being Fe and inevitable impurities,-   (52) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 10 to 19% by mass of Cr and 0.05 to 1.3% by mass of C,    the balance being Fe and inevitable impurities,-   (53) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the    balance being Fe and inevitable impurities, and-   (54) an iron-based sintered alloy having excellent machinability    with the composition consisting of 0.05 to 3% by mass of strontium    carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, and    one or more kinds selected from among 2 to 6% by mass of Cu, 0.1 to    0.5% by mass of Nb and 0.5 to 1.5% by mass of Al, the balance being    Fe and inevitable impurities.

The iron-based sintered alloys having excellent machinability, whichcontain 0.05 to 3% by mass of calcium carbonate, according to (1) to(27) of the present invention are produced by blending a calciumcarbonate powder having an average particle size of 0.1 to 30 μm withraw powders, mixing these powders and compacting the powder mixture toobtain a green compact, and sintering the resulting green compact in anatmosphere of a nonoxidizing gas such as vacuum, dissociated ammoniagas, N₂+5% H₂ gas mixture, endothermic gas or exothermic gas. The greencompact is particularly preferably sintered in an atmosphere of thenonoxidizing gas such as endothermic gas or exothermic gas. Theiron-based sintered alloy thus obtained has a structure in which CaCO₃is dispersed at grain boundary in a basis material of the iron-basedsintered alloy. The presence of CaCO₃ in the sintered compact obtainedby sintering the green compact can be confirmed by X-ray diffraction.

The iron-based sintered alloys having excellent machinability, whichcontain 0.05 to 3% by mass of strontium carbonate, according to (28) to(54) of the present invention are produced by blending a strontiumcarbonate powder having an average particle size of 0.1 to 30 μm withraw powders, mixing these powders and compacting the powder mixture toobtain a green compact, and sintering the resulting green compact in anatmosphere of a nonoxidizing gas such as vacuum, dissociated ammoniagas, N₂+5% H₂ gas mixture, endothermic gas or exothermic gas. The greencompact is particularly preferably sintered in an atmosphere of thenonoxidizing gas such as endothermic gas or exothermic gas. Theiron-based sintered alloy thus obtained has a structure in which SrCO₃is dispersed at grain boundary in a basis material of the iron-basedsintered alloy. The presence of SrCO₃ in the sintered compact obtainedby sintering the green compact can be confirmed by X-ray diffraction.

Therefore, the present invention is characterized by the followings:(55) a method for preparing the iron-based sintered alloy havingexcellent machinability according to any one of (1) to (27), whichcomprises compacting a raw powder mixture containing 0.05 to 3% by massof a calcium carbonate powder having an average particle size of 0.1 to30 μm as a raw powder to obtain a green compact and sintering theresulting green compact in a nonoxidizing gas atmosphere, and (56) amethod for preparing the iron-based sintered alloy having excellentmachinability according to any one of (28) to (54), which comprisescompacting a raw powder mixture containing 0.05 to 3% by mass of astrontium carbonate powder having an average particle size of 0.1 to 30μm as a raw powder to obtain a green compact and sintering the resultinggreen compact in a nonoxidizing gas atmosphere.

The average particle size of the calcium carbonate powder as the rawpowder was defined within a range from 0.1 to 30 μm by the followingreason. That is, when the average particle size of the calcium carbonatepowder exceeds 30 μm, a contact area between the calcium carbonatepowder and the basis material decreases and sufficient machinabilityimproving effect is not exerted. On the other hand, when the averageparticle size of the calcium carbonate powder is less than 0.1 μm, aforce of agglomeration increases, and thus the calcium carbonate powderis not uniformly dispersed in the basis material and furthermachinability improving effect is not exerted, and it is not preferred.

The average particle size of the strontium carbonate powder as the rawpowder was defined within a range from 0.1 to 30 μm by the followingreason. That is, when the average particle size of the strontiumcarbonate powder exceeds 30 μm, a contact area between the strontiumcarbonate powder and the basis material decreases and sufficientmachinability improving effect is not exerted. On the other hand, whenthe average particle size of the strontium carbonate powder is less than0.1 μm, a force of agglomeration increases, and thus the strontiumcarbonate powder is not uniformly dispersed in the basis material andfurther machinability improving effect is not exerted, and it is notpreferred.

The endothermic gas is a gas containing, as a main component, hydrogen,carbon monoxide and nitrogen, which is obtained by mixing a natural gas,propane, butane or coke oven gas with an air to obtain a gas mixture,and decomposing and converting the gas mixture while passing through aheated catalyst composed mainly of nickel. In this case, since thisreaction is an endothermic reaction, a catalyst layer must be heated.The exothermic gas is a gas containing nitrogen as a main component,hydrogen and carbon monoxide, which is obtained by semicombusting anatural gas, propane, butane or coke oven gas with air, and decomposingand converting the combustion gas while passing through a nickelcatalyst layer or charcoal layer. In this case, since the temperature ofthe catalyst increases due to combustion heat of the raw gas, it is notnecessary to externally heat the catalyst layer.

The sintering temperature, at which the iron-based sintered alloy havingexcellent machinability is sintered, is preferably from 1100 to 1300° C.(more preferably from 1110 to 1250° C.) and this sintering temperatureis the temperature which is generally known as a temperature at whichthe iron-based sintered alloy is sintered.

The reason why the composition of the CaCO₃ component and thecomposition of the SrCO₃ component in the iron-based sintered alloyhaving excellent machinability of the present invention were as limitedas described above will now be described.

CaCO₃ has such an effect that it exists at grain boundary and isuniformly dispersed in a basis material, thereby to improvemachinability. When the content is less than 0.05% by mass, sufficientmachinability improving effect is not exerted. On the other hand, evenwhen the content exceeds 3.0% by mass, further machinability improvingeffect is not exerted and the strength of the iron-based sintered alloyrather decreases, and therefore it is not preferred. Therefore, thecontent of CaCO₃ in the iron-based sintered alloy of the presentinvention was defined within a range from 0.05 to 3.0% by mass. Thecontent of CaCO₃ is more preferably within a range from 0.1 to 2% bymass.

SrCO₃ has such an effect that it exists at grain boundary and isuniformly dispersed in a basis material, thereby to improvemachinability. When the content is less than 0.05% by mass, sufficientmachinability improving effect is not exerted. On the other hand, evenwhen the content exceeds 3.0% by mass, further machinability improvingeffect is not exerted and the strength of the iron-based sintered alloyrather decreases, and therefore it is not preferred. Therefore, thecontent of SrCO₃ in the iron-based sintered alloy of the presentinvention was defined within a range from 0.05 to 3.0% by mass. Thecontent of SrCO₃ is more preferably within a range from 0.1 to 2% bymass.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred examples of the present invention will now be described withreference to the accompanying drawings. The present invention is notlimited to the following examples and, for example, constituent featuresof these examples may be appropriately combined with each other.

EXAMPLE 1

As raw powders, a CaCO₃ powder having an average particle size shown inTable 1, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm and a pure Fe powder having anaverage particle size of 80 μm were prepared. These raw powders wereblended according to the formulation shown in Table 1, mixed in a doublecorn mixer and compacted to obtain a green compact, and then theresulting green compact was sintered in an endothermic gas (ratio ofcomponents=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%)atmosphere under the conditions of a temperature of 1120° C. and aretention time of 20 minutes to obtain iron-based sintered alloys 1 to10 of the present invention, comparative sintered alloys 1 to 2, andconventional sintered alloys 1 to 3.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 1to 10 of the present invention, the comparative sintered alloys 1 to 2,and the conventional sintered alloys 1 to 3 were produced and thesecylindrical sintered alloy blocks for piercing test were repeatedlypierced until the drill is damaged, using a high-speed steel drillhaving a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.030 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 1.    Machinability was evaluated by the results.

TABLE 1 Component Component ratio of raw powder ratio of iron-based(mass %) sintered alloy (mass %) CaCO₃ powder Fe and Number of Averageparticle size is inevitable piercing Iron-based sintered alloy describedin parenthesis. Fe powder CaCO₃ impurities (times) Remarks Products ofthe 1  0.05 (0.1 μm) balance 0.03 balance 59 — present invention 2  0.2(0.1 μm) balance 0.18 balance 137 — 3  0.5 (0.6 μm) balance 0.48 balance155 — 4  1.0 (2 μm) balance 0.95 balance 203 — 5  1.3 (0.6 μm) balance1.26 balance 196 — 6  1.5 (2 μm) balance 1.48 balance 236 — 7  1.8 (18μm) balance 1.76 balance 213 — 8  2.1 (2 μm) balance 1.99 balance 176 —9  2.5 (18 μm) balance 2.43 balance 222 — 10   3.0 (30 μm) balance 2.97balance 310 — Comparative 1 0.02* (40 μm*) balance 0.01 balance 23 —products 2  3.5* (0.01 μm*) balance  3.45* balance 114 decrease instrength Conventional 1 CaMgSi₄: 1 balance CaMgSi₄: 1 balance 38 —products 2 MnS: 1 balance MnS: 0.97 balance 27 — 3 CaF₂: 1 balance CaF₂:1 balance 25 — The symbol * means the value which is not within thescope of the present invention.

As is apparent from the results shown in Table 1, the number of piercingof the cylindrical sintered alloy blocks for piercing test made of thesintered alloys 1 to 10 of the present invention is larger than that ofthe cylindrical sintered alloy blocks for piercing test made of theconventional sintered alloys 1 to 3 and therefore the sintered alloys ofthe present invention are excellent in machinability. However, thecomparative sintered alloy 1 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 2 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 2

As raw powders, a CaCO₃ powder having an average particle size shown inTable 2, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm and a Fe-0.6 mass % P powderhaving an average particle size of 80 μm were prepared. These rawpowders were blended according to the formulation shown in Table 2,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in an endothermic gas(ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂:39.1%) atmosphere under the conditions of a temperature of 1120° C. anda retention time of 20 minutes to obtain iron-based sintered alloys 11to 20 of the present invention, comparative sintered alloys 3 to 4, andconventional sintered alloys 4 to 6.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 11to 20 of the present invention, the comparative sintered alloys 3 to 4,and the conventional sintered alloys 4 to 6 were produced and thesecylindrical sintered alloy blocks for piercing test were repeatedlypierced until the drill is damaged, using a high-speed steel drillhaving a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.030 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 2.    Machinability was evaluated by the results.

TABLE 2 Component ratio of Component ratio of raw powder iron-basedsintered alloy (mass %) (mass %) CaCO₃ powder Fe Average particleFe-based and Number of Iron-based sintered size is described alloyinevitable piercing alloy in parenthesis. powder# CaCO₃ P impurities(times) Remarks Products of the 11  0.05 (0.1 μm) balance 0.03 0.55balance 51 — present invention 12  0.2 (0.1 μm) balance 0.18 0.58balance 119 — 13  0.5 (0.6 μm) balance 0.48 0.53 balance 158 — 14  1.0(2 μm) balance 0.95 0.53 balance 176 — 15  1.3 (0.6 μm) balance 1.280.57 balance 140 — 16  1.5 (2 μm) balance 1.48 0.57 balance 131 — 17 1.8 (18 μm) balance 1.76 0.54 balance 167 — 18  2.1 (2 μm) balance 1.990.53 balance 121 — 19  2.5 (18 μm) balance 2.42 0.55 balance 137 — 20 3.0 (30 μm) balance 2.97 0.55 balance 186 — Comparative 3 0.02* (40μm*) balance  0.01* 0.56 balance 27 — products 4  3.5* (0.01 μm*)balance  3.42* 0.54 balance 125 decrease in strength Conventional 4CaMgSi₄: 1 balance CaMgSi₄: 1 0.55 balance 33 — products 5 MnS: 1balance MnS: 0.97 0.55 balance 35 — 6 CaF₂: 1 balance CaF₂: 1 0.55balance 22 — The symbol * means the value which is not within the scopeof the present invention. #Fe-based alloy powder with the composition ofFe-0.6 mass % P

As is apparent from the results shown in Table 2, the number of piercingof the cylindrical sintered alloy blocks for piercing test made of thesintered alloys 11 to 20 of the present invention is larger than that ofthe cylindrical sintered alloy blocks for piercing test made of theconventional sintered alloys 4 to 6 and therefore the sintered alloys ofthe present invention are excellent in machinability. However, thecomparative sintered alloy 3 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 4 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 3

As raw powders, a CaCO₃ powder having an average particle size shown inTable 3, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe powder having an averageparticle size of 80 μm and a C powder having an average particle size of18 μm were prepared. These raw powders were blended according to theformulation shown in Table 3, mixed in a double corn mixer and compactedto obtain a green compact, and then the resulting green compact wassintered in an endothermic gas (ratio of components=H₂: 40.5%, CO:19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under theconditions of a temperature of 1120° C. and a retention time of 20minutes to obtain iron-based sintered alloys 21 to 30 of the presentinvention, comparative sintered alloys 5 to 6, and conventional sinteredalloys 7 to 9.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 21to 30 of the present invention, the comparative sintered alloys 5 to 6,and the conventional sintered alloys 7 to 9 were produced and thesecylindrical sintered alloy blocks for piercing test were repeatedlypierced until the drill is damaged, using a high-speed steel drillhaving a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.018 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 3.    Machinability was evaluated by the results.

TABLE 3 Component ratio of Component ratio of iron-based raw powder(mass %) sintered alloy (mass %) CaCO₃ powder Fe Average particle andNumber of Iron-based sintered size is described C Fe inevitable piercingalloy in parenthesis. powder powder CaCO₃ C impurities (times) RemarksProducts of the 21  0.05 (0.1 μm) 0.13 balance 0.03 0.11 balance 80 —present invention 22  0.2 (0.1 μm) 0.3 balance 0.17 0.24 balance 102 —23  0.5 (0.6 μm) 0.6 balance 0.47 0.54 balance 95 — 24  1.0 (2 μm) 0.8balance 0.94 0.55 balance 135 — 25  1.3 (0.6 μm) 1.1 balance 1.22 1.02balance 197 — 26  1.5 (2 μm) 1.1 balance 1.43 0.99 balance 208 — 27  1.8(18 μm) 1.1 balance 1.69 1.05 balance 191 — 28  2.1 (2 μm) 1.1 balance2.09 1.03 balance 220 — 29  2.5 (18 μm) 1.1 balance 2.3  1.03 balance174 — 30  3.0 (30 μm) 1.2 balance 2.91 1.15 balance 180 — Comparative 50.02* (40 μm*) 1.1 balance  0.01* 1.04 balance 22 — products 6  3.5*(0.01 μm*) 1.1 balance  3.38* 1.01 balance 126 decrease in strengthConventional 7 CaMgSi₄: 1 (10 μm) 1.1 balance CaMgSi₄: 1 1.04 balance 37— products 8 MnS: 1 (20 μm) 1.1 balance MnS: 0.97 1.04 balance 45 — 9CaF₂: 1 (36 μm) 1.1 balance CaF₂: 1 1.04 balance 29 — The symbol * meansthe value which is not within the scope of the present invention.

As is apparent from the results shown in Table 3, the number of piercingof the cylindrical sintered alloy blocks for piercing test made of thesintered alloys 21 to 30 of the present invention is larger than that ofthe cylindrical sintered alloy blocks for piercing test made of theconventional sintered alloys 7 to 9 and therefore the sintered alloys ofthe present invention are excellent in machinability. However, thecomparative sintered alloy 5 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 6 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 4

As raw powders, a CaCO₃ powder having an average particle size shown inTable 4, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe powder having an averageparticle size of 80 μm and a C powder having an average particle size of18 μm were prepared. These raw powders were blended according to theformulation shown in Table 4, mixed in a double corn mixer and compactedto obtain a green compact, and then the resulting green compact wassintered in an endothermic gas (ratio of components=H₂: 40.5%, CO:19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere under theconditions of a temperature of 1120° C. and a retention time of 20minutes and subjected to 20% Cu infiltration to obtain iron-basedsintered alloys 31 to 40 of the present invention, comparative sinteredalloys 7 to 8, and conventional sintered alloys 10 to 12.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 31to 40 of the present invention, the comparative sintered alloys 7 to 8,and the conventional sintered alloys 10 to 12 were produced and thesecylindrical sintered alloy blocks for piercing test were repeatedlypierced until the drill is damaged, using a high-speed steel drillhaving a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.018 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 4.    Machinability was evaluated by the results.

TABLE 4 Component ratio of iron-based sintered Component ratio of rawpowder (mass %) alloy (mass %) CaCO₃ powder Fe Number Average particleand of Iron-based sintered size is described Infiltration inevitablepiercing alloy in parenthesis. C powder Fe powder Cu CaCO₃ C Cuimpurities (times) Remarks Products of the 31  0.05 (0.1 μm) 0.13balance 20 0.05 0.12 19.5 balance 78 — present 32  0.2 (0.5 μm) 0.3balance 20 0.20 0.24 20.2 balance 126 — invention 33  0.5 (1 μm) 0.6balance 20 0.49 0.54 20.1 balance 186 — 34  1.0 (2 μm) 0.8 balance 200.97 0.75 19.6 balance 201 — 35  1.3 (0.5 μm) 1.1 balance 20 1.28 1.0519.9 balance 210 — 36  1.5 (2 μm) 1.1 balance 20 1.46 0.99 20.4 balance176 — 37  1.8 (18 μm) 1.1 balance 20 1.77 1.05 19.8 balance 197 — 38 2.1 (2 μm) 1.1 balance 20 2.09 1.07 20.0 balance 189 — 39  2.5 (18 μm)1.1 balance 20 2.45 1.07 19.7 balance 160 — 40  3.0 (30 μm) 1.2 balance20 2.96 1.15 19.9 balance 152 — Comparative 7 0.02* (40 μm*) 1.1 balance20  0.01* 1.04 20.3 balance 23 — products 8  3.5* (0.01 μm*) 1.1 balance20  3.45* 1.06 19.6 balance 112 decrease in strength Conventional 10CaMgSi₄: 1 (10 μm) 1.1 balance 20 CaMgSi₄: 1 1.04 19.8 balance 41 —products 11 MnS: 1 (20 μm) 1.1 balance 20 MnS: 0.97 1.04 19.8 balance 48— 12 CaF₂: 1 (36 μm) 1.1 balance 20 CaF₂: 1 1.04 19.9 balance 32 — Thesymbol * means the value which is not within the scope of the presentinvention.

As is apparent from the results shown in Table 4, the number of piercingof the cylindrical sintered alloy blocks for piercing test made of thesintered alloys 31 to 40 of the present invention is larger than that ofthe cylindrical sintered alloy blocks for piercing test made of theconventional sintered alloys 10 to 12 and therefore the sintered alloysof the present invention are excellent in machinability. However, thecomparative sintered alloy 7 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 8 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 5

As raw powders, a CaCO₃ powder having an average particle size shown inTable 5, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe powder having an averageparticle size of 80 μm, a Cu powder having an average particle size of25 μm and a C powder having an average particle size of 18 μm wereprepared. These raw powders were blended according to the formulationshown in Table 5, mixed in a double corn mixer and compacted to obtain agreen compact, and then the resulting green compact was sintered in anendothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%,CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of atemperature of 1120° C. and a retention time of 20 minutes to obtainiron-based sintered alloys 41 to 50 of the present invention,comparative sintered alloys 9 to 10, and conventional sintered alloys 13to 15.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 41to 50 of the present invention, the comparative sintered alloys 9 to 10,and the conventional sintered alloys 13 to 15 were produced and thesecylindrical sintered alloy blocks for piercing test were repeatedlypierced until the drill is damaged, using a high-speed steel drillhaving a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.030 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 5.    Machinability was evaluated by the results.

TABLE 5 Component ratio of Component ratio of raw powder (mass %)iron-based sintered alloy (mass %) CaCO₃ powder Fe Number Averageparticle and of Iron-based sintered size is described Cu C Fe inevitablepiercing alloy in parenthesis. powder powder powder CaCO₃ Cu Cimpurities (times) Remarks Products of the 41  0.05 (0.1 μm) 0.2 0.13balance 0.03 2.0 0.11 balance 53 — present 42  0.2 (0.1 μm) 2 0.25balance 0.17 2.1 0.22 balance 122 — invention 43  0.5 (0.6 μm) 2 0.98balance 0.47 1.9 0.87 balance 129 — 44  1.0 (2 μm) 2 0.7 balance 0.942.0 0.66 balance 235 — 45  1.3 (0.6 μm) 2 0.7 balance 1.22 2.0 0.64balance 250 — 46  1.5 (2 μm) 4 0.7 balance 1.43 4.0 0.65 balance 220 —47  1.8 (18 μm) 5.8 0.7 balance 1.69 5.7 0.65 balance 203 — 48  2.1 (2μm) 4 0.7 balance 2.09 3.9 0.64 balance 190 — 49  2.5 (18 μm) 2 0.98balance 2.3  2.0 0.88 balance 145 — 50  3.0 (30 μm) 2 1.2 balance 2.912.0 1.15 balance 179 — Comparative 9 0.02* (40 μm*) 2 0.7 balance  0.01*1.9 0.65 balance 10 — products 10  3.5* (0.01 μm*) 2 0.7 balance  3.45*2.0 0.64 balance 108 decrease in strength Conventional 13 CaMgSi₄: 1 20.7 balance CaMgSi₄: 1 2.0 0.66 balance 20 — products 14 MnS: 1 2 0.7balance MnS: 0.97 2.0 0.64 balance 14 — 15 CaF₂: 1 2 0.7 balance CaF₂: 12.0 0.64 balance 9 — The symbol * means the value which is not withinthe scope of the present invention.

As is apparent from the results shown in Table 5, the number of piercingof the cylindrical sintered alloy blocks for piercing test made of thesintered alloys 41 to 50 of the present invention is larger than that ofthe cylindrical sintered alloy blocks for piercing test made of theconventional sintered alloys 13 to 15 and therefore the sintered alloysof the present invention are excellent in machinability. However, thecomparative sintered alloy 9 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 10 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 6

As raw powders, a CaCO₃ powder having an average particle size shown inTable 6, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a partially diffused Fe-basedalloy powder having an average particle size of 80 μm with thecomposition of Fe-1.5% Cu-4.0% Ni-0.5% Mo and a C powder having anaverage particle size of 18 μm were prepared. These raw powders wereblended according to the formulation shown in Table 6, mixed in a doublecorn mixer and compacted to obtain a green compact, and then theresulting green compact was sintered in an endothermic gas (ratio ofcomponents=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%)atmosphere under the conditions of a temperature of 1120° C. and aretention time of 20 minutes to obtain iron-based sintered alloys 51 to60 of the present invention, comparative sintered alloys 11 to 12, andconventional sintered alloys 16 to 18.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 51to 60 of the present invention, the comparative sintered alloys 11 to12, and the conventional sintered alloys 16 to 18 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 6.    Machinability was evaluated by the results.

TABLE 6 Component ratio Component ratio of raw powder (mass %) ofiron-based sintered alloy (mass %) CaCO₃ powder Fe Number Averageparticle Fe-based and of Iron-based sintered size is described C alloyinevitable piercing alloy in parenthesis. powder powder# CaCO₃ Cu C NiMo impurities (times) Remarks Products of the 51  0.05 (0.1 μm) 0.13balance 0.03 1.5 0.11 3.9 0.50 balance 48 — present 52  0.2 (0.1 μm)0.25 balance 0.18 1.5 0.19 4.0 0.50 balance 153 — invention 53  0.5 (0.6μm) 0.98 balance 0.46 1.5 0.85 4.0 0.50 balance 214 — 54  1.0 (2 μm) 0.5balance 0.96 1.4 0.47 4.1 0.52 balance 300 — 55  1.3 (0.6 μm) 0.5balance 1.25 1.5 0.45 4.0 0.50 balance 287 — 56  1.5 (2 μm) 0.5 balance1.45 1.5 0.45 4.0 0.50 balance 324 — 57  1.8 (18 μm) 0.5 balance 1.721.5 0.47 4.0 0.49 balance 274 — 58  2.1 (2 μm) 0.5 balance 1.89 1.6 0.473.8 0.50 balance 257 — 59  2.5 (18 μm) 1.0 balance 2.32 1.5 0.90 4.00.50 balance 231 — 60  3.0 (30 μm) 1.2 balance 2.89 1.5 1.17 4.0 0.50balance 267 — Comparative 11 0.02* (40 μm*) 0.5 balance  0.01* 1.5 0.434.1 0.50 balance 5 — products 12  3.5* (0.01 μm*) 0.5 balance  3.45* 1.50.44 4.0 0.51 balance 87 decrease in strength Conventional 16 CaMgSi₄: 10.5 balance CaMgSi₄: 1 1.5 0.46 4.0 0.50 balance 17 — products 17 MnS: 10.5 balance MnS: 0.97 1.5 0.47 4.0 0.50 balance 35 — 18 CaF₂: 1 0.5balance CaF₂: 1 1.5 0.45 4.0 0.48 balance 8 — The symbol * means thevalue which is not within the scope of the present invention. #partiallydiffused Fe-based alloy powder having an average particle size of 80 μmwith the composition of Fe-1.5% Cu-4.0% Ni-0.5% Mo

As is apparent from the results shown in Table 6, the number of piercingof the cylindrical sintered alloy blocks for piercing test made of thesintered alloys 51 to 60 of the present invention is larger than that ofthe cylindrical sintered alloy blocks for piercing test made of theconventional sintered alloys 16 to 18 and therefore the sintered alloysof the present invention are excellent in machinability. However, thecomparative sintered alloy 11 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 12 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 7

As raw powders, a CaCO₃ powder having an average particle size shown inTable 7, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe-based alloy powder havingan average particle size of 80 μm with the composition of Fe-1.5% Mo anda C powder having an average particle size of 18 μm were prepared. Theseraw powders were blended according to the formulation shown in Table 7,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in an endothermic gas(ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂:39.1%) atmosphere under the conditions of a temperature of 1120° C. anda retention time of 20 minutes to obtain iron-based sintered alloys 61to 70 of the present invention, comparative sintered alloys 13 to 14,and conventional sintered alloys 19 to 21.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 61to 70 of the present invention, the comparative sintered alloys 13 to14, and the conventional sintered alloys 19 to 21 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 7.    Machinability was evaluated by the results.

TABLE 7 Component Component ratio of ratio of raw powder (mass %)iron-based sintered alloy (mass %) CaCO₃ powder Fe Number Averageparticle Fe-based and of Iron-based sintered size is described C alloyinevitable piercing alloy in parenthesis. powder powder# CaCO₃ C Moimpurities (times) Remarks Products of the 61  0.05 (0.1 μm) 0.13balance 0.03 0.11 1.50 balance 48 — present invention 62  0.2 (0.1 μm)0.25 balance 0.19 0.19 1.48 balance 85 — 63  0.5 (0.6 μm) 0.98 balance0.48 0.85 1.50 balance 71 — 64  1.0 (2 μm) 0.5 balance 0.97 0.46 1.50balance 214 — 65  1.3 (0.6 μm) 0.5 balance 1.27 0.47 1.50 balance 225 —66  1.5 (2 μm) 0.5 balance 1.44 0.45 1.51 balance 201 — 67  1.8 (18 μm)0.5 balance 1.72 0.45 1.46 balance 228 — 68  2.1 (2 μm) 0.5 balance 1.950.44 1.50 balance 219 — 69  2.5 (18 μm) 1.0 balance 2.39 0.90 1.50balance 170 — 70  3.0 (30 μm) 1.2 balance 2.91 1.17 1.53 balance 148 —Comparative 13 0.02* (40 μm*) 0.5 balance  0.01* 0.43 1.51 balance 12 —products 14  3.5* (0.01 μm*) 0.5 balance  3.45* 0.44 1.50 balance 81decrease in strength Conventional 19 CaMgSi₄: 1 0.5 balance CaMgSi₄: 10.46 1.51 balance 20 — products 20 MnS: 1 0.5 balance MnS: 0.97 0.471.50 balance 23 — 21 CaF₂: 1 0.5 balance CaF₂: 1 0.44 1.48 balance 16 —The symbol * means the value which is not within the scope of thepresent invention. #Fe-based alloy powder having an average particlesize of 80 μm with the composition of Fe-1.5% Mo

As is apparent from the results shown in Table 7, the number of piercingof the cylindrical sintered alloy blocks for piercing test made of thesintered alloys 61 to 70 of the present invention is larger than that ofthe cylindrical sintered alloy blocks for piercing test made of theconventional sintered alloys 19 to 21 and therefore the sintered alloysof the present invention are excellent in machinability. However, thecomparative sintered alloy 13 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 14 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 8

As raw powders, a CaCO₃ powder having an average particle size shown inTable 8, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe-based alloy powder havingan average particle size of 80 μm with the composition of Fe-3.0%Cr-0.5% Mo and a C powder having an average particle size of 18 μm wereprepared. These raw powders were blended according to the formulationshown in Table 8, mixed in a double corn mixer and compacted to obtain agreen compact, and then the resulting green compact was sintered in anN₂+5% H₂ gas mixture atmosphere under the conditions of a temperature of1120° C. and a retention time of 20 minutes to obtain iron-basedsintered alloys 71 to 80 of the present invention, comparative sinteredalloys 15 to 16, and conventional sintered alloys 22 to 24.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 71to 80 of the present invention, the comparative sintered alloys 15 to16, and the conventional sintered alloys 22 to 24 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 8.    Machinability was evaluated by the results.

TABLE 8 Component Component ratio of ratio of raw powder (mass %)iron-based sintered alloy (mass %) CaCO₃ powder Fe Number Averageparticle Fe-based and of Iron-based sintered size is described C alloyinevitable piercing alloy in parenthesis. powder powder# CaCO₃ C Cr Moimpurities (times) Remarks Products of the 71  0.05 (0.1 μm) 0.13balance 0.03 0.11 3.0 0.50 balance 31 — present 72  0.2 (0.1 μm) 0.25balance 0.19 0.19 3.0 0.50 balance 105 — invention 73  0.5 (0.6 μm) 0.98balance 0.48 0.85 3.0 0.49 balance 121 — 74  1.0 (2 μm) 0.5 balance 0.970.47 3.0 0.50 balance 163 — 75  1.3 (0.6 μm) 0.5 balance 1.27 0.45 2.90.50 balance 186 — 76  1.5 (2 μm) 0.5 balance 1.44 0.45 3.0 0.51 balance151 — 77  1.8 (18 μm) 0.5 balance 1.72 0.44 3.0 0.49 balance 185 — 78 2.1 (2 μm) 0.5 balance 1.95 0.44 3.1 0.50 balance 196 — 79  2.5 (18 μm)1.0 balance 2.39 0.90 3.0 0.50 balance 103 — 80  3.0 (30 μm) 1.2 balance2.91 1.17 3.0 0.50 balance 88 — Comparative 15 0.02* (40 μm*) 0.5balance  0.01* 0.43 3.1 0.50 balance 3 — products 16  3.5* (0.01 μm*)0.5 balance  3.45* 0.45 3.0 0.51 balance 89 decrease in strengthConventional 22 CaMgSi₄: 1 0.5 balance CaMgSi₄: 1 0.46 3.0 0.50 balance16 — products 23 MnS: 1 0.5 balance MnS: 0.97 0.47 3.1 0.50 balance 13 —24 CaF₂: 1 0.5 balance CaF₂: 1 0.44 3.0 0.50 balance 8 — The symbol *means the value which is not within the scope of the present invention.#Fe-based alloy powder having a particle size of 80 μm with thecomposition of Fe-3.0% Cr-0.5% Mo

As is apparent from the results shown in Table 8, the number of piercingof the cylindrical sintered alloy blocks for piercing test made of thesintered alloys 71 to 80 of the present invention is larger than that ofthe cylindrical sintered alloy blocks for piercing test made of theconventional sintered alloys 22 to 24 and therefore the sintered alloysof the present invention are excellent in machinability. However, thecomparative sintered alloy 15 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 16 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 9

As raw powders, a CaCO₃ powder having an average particle size shown inTable 9, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe-based alloy powder havingan average particle size of 80 μm with the composition of Fe-3.0%Cr-0.5% Mo, a Ni powder having an average particle size of 3 μm and a Cpowder having an average particle size of 18 μm were prepared. These rawpowders were blended according to the formulation shown in Table 9,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in an N₂+5% H₂ gasmixture atmosphere under the conditions of a temperature of 1120° C. anda retention time of 20 minutes to obtain iron-based sintered alloys 81to 90 of the present invention, comparative sintered alloys 17 to 18,and conventional sintered alloys 25 to 27.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 81to 90 of the present invention, the comparative sintered alloys 17 to18, and the conventional sintered alloys 25 to 27 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 9.    Machinability was evaluated by the results.

TABLE 9 Component ratio of Component ratio of raw powder (mass %)iron-based sintered alloy (mass %) CaCO₃ powder Fe Number Averageparticle Fe-based and of Iron-based sintered size is described alloyinevitable piercing alloy in parenthesis. C powder Ni powder powder#CaCO₃ C Ni Cr Mo impurities (times) Remarks Products of the 81  0.05(0.1 μm) 0.13 0.2 balance 0.03 0.11 0.2 3.0 0.50 balance 65 — present 82 0.2 (0.1 μm) 0.25 2 balance 0.19 0.19 2.0 3.0 0.50 balance 93 —invention 83  0.5 (0.6 μm) 0.98 4 balance 0.48 0.85 4.0 3.0 0.49 balance89 — 84  1.0 (2 μm) 0.5 4 balance 0.97 0.47 4.0 3.0 0.50 balance 135 —85  1.3 (0.6 μm) 0.5 4 balance 1.27 0.45 3.9 2.9 0.50 balance 112 — 86 1.5 (2 μm) 0.5 4 balance 1.44 0.45 4.0 3.0 0.51 balance 125 — 87  1.8(18 μm) 0.5 4 balance 1.72 0.44 4.0 3.0 0.49 balance 140 — 88  2.1 (2μm) 0.5 6 balance 1.95 0.44 6.0 3.1 0.50 balance 177 — 89  2.5 (18 μm)1.0 8 balance 2.39 0.90 7.9 3.0 0.50 balance 133 — 90  3.0 (30 μm) 1.29.8 balance 2.91 1.17 9.8 3.0 0.50 balance 109 — Comparative 17 0.02*(40 μm*) 0.5 4 balance  0.01* 0.43 4.1 3.1 0.50 balance 3 — products 18 3.5* (0.01 μm*) 0.5 4 balance  3.45* 0.45 4.0 3.0 0.51 balance 101decrease in strength Conventional 25 CaMgSi₄: 1 0.5 4 balance CaMgSi₄: 10.46 4.0 3.0 0.50 balance 6 — products 26 MnS: 1 0.5 4 balance MnS: 0.970.47 4.0 3.1 0.50 balance 8 — 27 CaF₂: 1 0.5 4 balance CaF₂: 1 0.44 4.03.0 0.50 balance 8 — The symbol * means the value which is not withinthe scope of the present invention. #Fe-based alloy powder having aparticle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo

As is apparent from the results shown in Table 9, the number of piercingof the cylindrical sintered alloy blocks for piercing test made of thesintered alloys 81 to 90 of the present invention is larger than that ofthe cylindrical sintered alloy blocks for piercing test made of theconventional sintered alloys 25 to 27 and therefore the sintered alloysof the present invention are excellent in machinability. However, thecomparative sintered alloy 17 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 18 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 10

As raw powders, a CaCO₃ powder having an average particle size shown inTable 10, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe-based alloy powder havingan average particle size of 80 μm with the composition of Fe-3.0%Cr-0.5% Mo, a Cu powder having an average particle size of 25 μm, a Nipowder having an average particle size of 3 μm and a C powder having anaverage particle size of 18 μm were prepared. These raw powders wereblended according to the formulation shown in Table 10, mixed in adouble corn mixer and compacted to obtain a green compact, and then theresulting green compact was sintered in an N₂+5% H₂ gas mixtureatmosphere under the conditions of a temperature of 1120° C. and aretention time of 20 minutes to obtain iron-based sintered alloys 91 to100 of the present invention, comparative sintered alloys 19 to 20, andconventional sintered alloys 28 to 30.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 91to 100 of the present invention, the comparative sintered alloys 19 to20, and the conventional sintered alloys 28 to 30 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 10.    Machinability was evaluated by the results.

TABLE 10 Component ratio of raw powder (mass %) CaCO₃ powder Componentratio of iron-based sintered alloy (mass %) Number Average particle CuFe- Fe and of Iron-based size is described pow- C Ni based inevitablepiercing sintered alloy in parenthesis. der powder powder alloy # CaCO₃Cu C Ni Cr Mo impurities (times) Remarks Products 91  0.05 (0.1 μm) 0.20.13 0.2 balance 0.03 0.2 0.11 0.2 3.0 0.50 balance 34 — of the 92  0.2(0.1 μm) 2 0.25 2 balance 0.19 2.1 0.19 2.0 3.0 0.50 balance 87 —present 93  0.5 (0.6 μm) 2 0.98 4 balance 0.48 1.9 0.85 4.0 3.0 0.49balance 95 — invention 94  1.0 (2 μm) 2 0.5 4 balance 0.97 2.0 0.47 4.03.0 0.50 balance 150 — 95  1.3 (0.6 μm) 2 0.5 4 balance 1.27 2.0 0.453.9 2.9 0.50 balance 138 — 96  1.5 (2 μm) 4 0.5 4 balance 1.44 4.0 0.454.0 3.0 0.51 balance 143 — 97  1.8 (18 μm) 5.8 0.5 4 balance 1.72 5.80.44 4.0 3.0 0.49 balance 139 — 98  2.1 (2 μm) 4 0.5 6 balance 1.95 4.00.44 6.0 3.1 0.50 balance 155 — 99  2.5 (18 μm) 2 1.0 8 balance 2.39 2.00.90 7.9 3.0 0.50 balance 132 — 100  3.0 (30 μm) 2 1.2 9.8 balance 2.912.0 1.17 9.8 3.0 0.50 balance 129 — Com- 19 0.02* (40 μm*) 2 0.5 4balance  0.01* 1.9 0.43 4.1 3.0 0.50 balance 2 — parative 20  3.5* (0.01μm*) 2 0.5 4 balance  3.45* 2.0 0.45 4.0 3.0 0.51 balance 119 decreaseproducts in strength Con- 28 CaMgSi₄: 1 2 0.5 4 balance CaMgSi₄: 1 2.00.46 4.0 3.0 0.50 balance 8 — ventional 29 MnS: 1 2 0.5 4 balance MnS:0.97 2.0 0.47 4.0 3.1 0.50 balance 4 — products 30 CaF₂: 1 2 0.5 4balance CaF₂: 1 2.0 0.44 4.0 3.0 0.50 balance 11 — The symbol * meansthe value which is not within the scope of the present invention.*Fe-based alloy powder having a particle size of 80 μm with thecomposition of Fe-3.0% Cr-0.5% Mo

As is apparent from the results shown in Table 10, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 91 to 100 of the present invention is larger thanthat of the cylindrical sintered alloy blocks for piercing test made ofthe conventional sintered alloys 28 to 30 and therefore the sinteredalloys of the present invention are excellent in machinability. However,the comparative sintered alloy 19 containing CaCO₃ in the content ofless than the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 20 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 11

As raw powders, a CaCO₃ powder having an average particle size shown inTable 11, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe powder having an averageparticle size of 80 μm, a Ni powder having an average particle size of 3μm and a C powder having an average particle size of 18 μm wereprepared. These raw powders were blended according to the formulationshown in Table 11, mixed in a double corn mixer and compacted to obtaina green compact, and then the resulting green compact was sintered in anendothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%,CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of atemperature of 1120° C. and a retention time of 20 minutes to obtainiron-based sintered alloys 101 to 110 of the present invention,comparative sintered alloys 21 to 22, and conventional sintered alloys31 to 33.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 101to 110 of the present invention, the comparative sintered alloys 21 to22, and the conventional sintered alloys 31 to 33 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.009 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 11.    Machinability was evaluated by the results.

TABLE 11 Component ratio of raw powder (mass %) Component ratio ofiron-based CaCO₃ powder sintered alloy (mass %) Average particle Fe andNumber of Iron-based sintered size is described C Ni Fe inevitablepiercing alloy in parenthesis. powder powder powder CaCO₃ C Niimpurities (times) Remarks Products of 101  0.05 (0.1 μm) 0.13 0.2balance 0.03 0.11 0.2 balance 43 — the present 102  0.2 (0.1 μm) 0.25 1balance 0.19 0.19 1.0 balance 84 — invention 103  0.5 (0.6 μm) 0.98 3balance 0.48 0.93 2.9 balance 79 — 104  1.0 (2 μm) 0.5 3 balance 0.970.44 3.0 balance 128 — 105  1.3 (0.6 μm) 0.5 3 balance 1.27 0.44 3.0balance 114 — 106  1.5 (2 μm) 0.5 3 balance 1.44 0.45 3.0 balance 202 —107  1.8 (18 μm) 0.5 3 balance 1.72 0.45 3.0 balance 187 — 108  2.1 (2μm) 0.5 6 balance 1.95 0.45 6.0 balance 168 — 109  2.5 (18 μm) 1.0 8balance 2.39 0.90 8.0 balance 126 — 110  3.0 (30 μm) 1.2 9.8 balance2.91 1.11 9.8 balance 99 — Comparative 21 0.02* (40 μm*) 0.5 3 balance0.01* 0.45 3.0 balance 5 — products 22  3.5* (0.01 μm*) 0.5 3 balance3.45* 0.45 3.0 balance 143 decrease in strength Conventional 31 CaMgSi₄:1 0.5 3 balance CaMgSi₄: 1 0.44 2.9 balance 17 — products 32 MnS: 1 0.54 balance MnS: 0.97 0.45 3.0 balance 20 — 33 CaF₂: 1 0.5 4 balance CaF₂:1 0.44 3.0 balance 12 — The symbol * means the value which is not withinthe scope of the present invention.

As is apparent from the results shown in Table 11, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 101 to 110 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 31 to 33 and therefore thesintered alloys of the present invention are excellent in machinability.However, the comparative sintered alloy 21 containing CaCO₃ in thecontent of less than the range defined in the present invention isinferior in machinability because of small number of piercing, while thecomparative sintered alloy 22 containing CaCO₃ in the content of morethan the range defined in the present invention is excellent inmachinability because of large number of piercing, but shows drasticallydecreased deflection strength, and therefore it is not preferred.

EXAMPLE 12

As raw powders, a CaCO₃ powder having an average particle size shown inTable 12, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe powder having an averageparticle size of 80 μm, a Ni powder having an average particle size of 3μm, a Mo powder having an average particle size of 3 μm and a C powderhaving an average particle size of 18 μm were prepared. These rawpowders were blended according to the formulation shown in Table 12,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in an endothermic gas(ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂:39.1%) atmosphere under the conditions of a temperature of 1120° C. anda retention time of 20 minutes to obtain iron-based sintered alloys 111to 120 of the present invention, comparative sintered alloys 23 to 24,and conventional sintered alloys 34 to 36.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 111to 120 of the present invention, the comparative sintered alloys 23 to24, and the conventional sintered alloys 34 to 36 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.009 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 12.    Machinability was evaluated by the results.

TABLE 12 Component ratio of raw powder (mass %) CaCO₃ powder Componentratio of iron-based sintered alloy Average (mass %) Number particle sizeis Fe and of Iron-based sintered described in C Ni Mo Fe inevitablepiercing alloy parenthesis. powder powder powder powder CaCO₃ C Ni Moimpurities (times) Remarks Products of the 111  0.05 (0.1 μm) 0.13 0.20.2 balance 0.03 0.11 0.2 0.2 balance 55 — present 112  0.2 (0.1 μm)0.25 1 0.3 balance 0.19 0.19 1.0 0.3 balance 91 — invention 113  0.5(0.6 μm) 0.98 4 0.5 balance 0.48 0.91 4.0 0.5 balance 103 — 114  1.0 (2μm) 0.6 4 0.5 balance 0.97 0.55 4.0 0.5 balance 170 — 115  1.3 (0.6 μm)0.6 4 0.5 balance 1.27 0.56 4.0 0.5 balance 227 — 116  1.5 (2 μm) 0.6 41 balance 1.44 0.54 3.9 1.0 balance 198 — 117  1.8 (18 μm) 0.6 4 3balance 1.72 0.54 3.9 2.7 balance 164 — 118  2.1 (2 μm) 0.6 6 4.8balance 1.95 0.55 6.0 4.8 balance 144 — 119  2.5 (18 μm) 1.0 8 0.5balance 2.39 0.92 8.0 0.5 balance 159 — 120  3.0 (30 μm) 1.2 9.8 0.5balance 2.91 1.14 9.8 0.5 balance 166 — Comparative 23 0.02* (40 μm*)0.6 4 0.5 balance 0.01* 0.54 4.0 0.5 balance 11 — products 24  3.5*(0.01 μm*) 0.6 4 0.5 balance 3.45* 0.54 4.0 0.5 balance 91 decrease instrength Conventional 34 CaMgSi₄: 1 0.6 4 0.5 balance CaMgSi₄: 1 0.544.0 0.5 balance 22 — products 35 MnS: 1 0.6 4 0.5 balance MnS: 0.97 0.554.0 0.5 balance 31 — 36 CaF₂: 1 0.6 4 0.5 balance CaF₂: 1 0.55 4.0 0.5balance 28 — The symbol * means the value which is not within the scopeof the present invention.

As is apparent from the results shown in Table 12, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 111 to 120 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 34 to 36 and therefore thesintered alloys of the present invention are excellent in machinability.However, the comparative sintered alloy 23 containing CaCO₃ in thecontent of less than the range defined in the present invention isinferior in machinability because of small number of piercing, while thecomparative sintered alloy 24 containing CaCO₃ in the content of morethan the range defined in the present invention is excellent inmachinability because of large number of piercing, but shows drasticallydecreased deflection strength, and therefore it is not preferred.

EXAMPLE 13

As raw powders, a CaCO₃ powder having an average particle size shown inTable 13, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe powder having an averageparticle size of 80 μm, a Ni powder having an average particle size of 3μm, a Cu powder having an average particle size of 25 μm and a C powderhaving an average particle size of 18 μm were prepared. These rawpowders were blended according to the formulation shown in Table 13,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in an endothermic gas(ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂:39.1%) atmosphere under the conditions of a temperature of 1120° C. anda retention time of 20 minutes to obtain iron-based sintered alloys 121to 130 of the present invention, comparative sintered alloys 25 to 26,and conventional sintered alloys 37 to 39.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 121to 130 of the present invention, the comparative sintered alloys 25 to26, and the conventional sintered alloys 37 to 39 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.009 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 13.    Machinability was evaluated by the results.

TABLE 13 Component ratio of raw powder (mass %) CaCO₃ powder Componentratio of iron-based sintered alloy Average (mass %) Number particle sizeis Fe and of Iron-based sintered described in Cu C Ni Fe inevitablepiercing alloy parenthesis. powder powder powder powder CaCO₃ Cu C Niimpurities (times) Remarks Products of the 121  0.05 (0.1 μm) 0.2 0.130.2 balance 0.03 0.2 0.11 0.2 balance 46 — present 122  0.2 (0.1 μm) 10.25 1 balance 0.17 1.0 0.21 1.0 balance 104 — invention 123  0.5 (0.6μm) 1 0.98 3 balance 0.47 1.0 0.91 3.0 balance 136 — 124  1.0 (2 μm) 10.6 3 balance 0.94 0.99 0.55 3.0 balance 157 — 125  1.3 (0.6 μm) 2 0.8 3balance 1.22 1.0 0.54 3.0 balance 180 — 126  1.5 (2 μm) 4 0.6 3 balance1.43 4.0 0.55 2.9 balance 166 — 127  1.8 (18 μm) 5.8 0.6 3 balance 1.695.7 0.56 3.0 balance 192 — 128  2.1 (2 μm) 1 0.6 6 balance 1.09 1.0 0.556.0 balance 153 — 129  2.5 (18 μm) 1 1.0 8 balance 2.3 1.0 0.91 8.0balance 193 — 130  3.0 (30 μm) 1 1.2 9.8 balance 2.91 1.0 1.13 9.8balance 179 — Comparative 25 0.02* (40 μm*) 1 0.6 3 balance 0.01* 1.00.55 3.0 balance 7 — products 26  3.5* (0.01 μm*) 1 0.6 3 balance 3.45*1.0 0.55 3.0 balance 79 decrease in strength Conventional 37 CaMgSi₄: 11 0.6 3 balance CaMgSi₄: 1 1.0 0.55 3.0 balance 12 — products 38 MnS: 11 0.6 3 balance MnS: 0.97 1.0 0.54 3.0 balance 15 — 39 CaF₂: 1 1 0.6 3balance CaF₂: 1 1.0 0.55 3.0 balance 9 — The symbol * means the valuewhich is not within the scope of the present invention.

As is apparent from the results shown in Table 13, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 121 to 130 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 37 to 39 and therefore thesintered alloys of the present invention are excellent in machinability.However, the comparative sintered alloy 25 containing CaCO₃ in thecontent of less than the range defined in the present invention isinferior in machinability because of small number of piercing, while thecomparative sintered alloy 26 containing CaCO₃ in the content of morethan the range defined in the present invention is excellent inmachinability because of large number of piercing, but shows drasticallydecreased deflection strength, and therefore it is not preferred.

EXAMPLE 14

As raw powders, a CaCO₃ powder having an average particle size shown inTable 14, a CaMgSiO₄ powder having an average particle size of 10 μm, aMnS powder having an average particle size of 20 μm, a CaF₂ powderhaving an average particle size of 36 μm, a Fe powder having an averageparticle size of 80 μm, a Cu—P powder having an average particle size of25 μm and a C powder having an average particle size of 18 μm wereprepared. These raw powders were blended according to the formulationshown in Table 14, mixed in a double corn mixer and compacted to obtaina green compact, and then the resulting green compact was sintered in anendothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%,CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of atemperature of 1120° C. and a retention time of 20 minutes to obtainiron-based sintered alloys 131 to 140 of the present invention,comparative sintered alloys 27 to 28, and conventional sintered alloys40 to 42.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 131to 140 of the present invention, the comparative sintered alloys 27 to28, and the conventional sintered alloys 40 to 42 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.009 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 14.    Machinability was evaluated by the results.

TABLE 14 Component ratio of iron-based Component ratio of raw powder(mass %) sintered alloy CaCO₃ powder (mass %) Number Average particle Feand of Iron-based sintered size is described C Cu-P Fe inevitablepiercing alloy in parenthesis. powder powder powder CaCO₃ C Cu Pimpurities (times) Remarks Products 131  0.05 (0.1 μm) 1.0 0.7 balance0.03 0.91 0.6 0.1 balance 77 — of the 132  0.2 (0.1 μm) 1.5 1.2 balance0.19 1.44 1.1 0.1 balance 73 — present 133  0.5 (0.6 μm) 1.5 1.8 balance0.48 1.46 1.6 0.2 balance 114 — invention 134  1.0 (2 μm) 2.0 1.8balance 0.97 1.95 1.6 0.2 balance 203 — 135  1.3 (0.6 μm) 2.0 2.8balance 1.27 1.93 2.5 0.3 balance 231 — 136  1.5 (2 μm) 2.0 2.8 balance1.44 1.93 2.5 0.3 balance 211 — 137  1.8 (18 μm) 2.0 3.3 balance 1.721.96 3 0.3 balance 274 — 138  2.1 (2 μm) 2.5 6.0 balance 1.95 2.48 5.40.6 balance 177 — 139  2.5 (18 μm) 2.5 8.0 balance 2.39 2.45 5 0.6balance 229 — 140  3.0 (30 μm) 3.0 9.0 balance 2.91 2.99 8.2 0.8 balance310 — Comparative 27 0.02* (40 μm*) 1 2.8 balance 0.01* 0.45 2.5 0.3balance 2 — products 28  3.5* (0.01 μm*) 1 2.8 balance 3.43* 0.45 2.50.3 balance 198 decrease in strength Conventional 40 CaMgSi₄: 1 1 2.8balance CaMgSi₄: 1 0.44 2.9 0.3 balance 32 — products 41 MnS: 1 1 2.8balance MnS: 0.97 0.45 3.0 0.3 balance 53 — 42 CaF₂: 1 1 2.8 balanceCaF₂: 1 0.44 3.0 0.3 balance 40 — The symbol * means the value which isnot within the scope of the present invention.

As is apparent from the results shown in Table 14, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 131 to 140 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 40 to 42 and therefore thesintered alloys of the present invention are excellent in machinability.However, the comparative sintered alloy 27 containing CaCO₃ in thecontent of less than the range defined in the present invention isinferior in machinability because of small number of piercing, while thecomparative sintered alloy 28 containing CaCO₃ in the content of morethan the range defined in the present invention is excellent inmachinability because of large number of piercing, but shows drasticallydecreased deflection strength, and therefore it is not preferred.

EXAMPLE 15

As raw powders, a CaCO₃ powder having an average particle size of 0.6μm, a CaF₂ powder having an average particle size of 36 μm and a Fe-6%Cr-6% Mo-9% W-3% V-10% Co-1.5% C powder having an average particle sizeof 80 μm were prepared. These raw powders were blended according to theformulation shown in Table 15, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in a dissociated ammonia gas atmosphere under theconditions of a temperature of 1150° C. and a retention time of 60minutes to obtain an iron-based sintered alloy 141 of the presentinvention, comparative sintered alloys 29 to 30, and a conventionalsintered alloy 43.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 141of the present invention, the comparative sintered alloys 29 to 30, andthe conventional sintered alloy 43 were produced and these cylindricalsintered alloy blocks for piercing test were repeatedly pierced untilthe drill is damaged, using a high-speed steel drill having a diameterof 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 15.    Machinability was evaluated by the results.

TABLE 15 Component ratio of raw powder (mass %) Fe-6% Cr- CaCO₃ powder6% Mo- Component ratio Average particle 9% W-3% V- of iron-basedsintered alloy (mass %) size 10% Co- Fe and Number of Iron-basedsintered is described in 1.5% C inevitable piercing alloy parenthesis.powder CaCO₃ C Cr Mo W Co V impurities (times) Remarks Product of the141  0.5 (0.6 μm) balance 0.48 1.5 6 6 9 10 3 balance 158 — presentinvention Comparative 29 0.02* (40 μm*) balance 0.01* 1.5 6 6 9 10 3balance 18 — products 30  3.5* (0.01 μm*) balance 3.43* 1.5 6 6 9 10 3balance 127 decrease in strength Conventional 43 CaF₂: 1 balance CaF₂: 11.5 6 6 9 10 3 balance 26 — product The symbol * means the value whichis not within the scope of the present invention.

As is apparent from the results shown in Table 15, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 141 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 43 and therefore the sintered alloy of thepresent invention is excellent in machinability. However, thecomparative sintered alloy 29 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 30 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 16

As raw powders, a CaCO₃ powder having an average particle size of 0.6μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-basedalloy powder having an average particle size of 80 μm with thecomposition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having an averageparticle size of 80 μm, a Ni powder having an average particle size of 3μm, a Mo powder having an average particle size of 3 μm, a Co-basedalloy powder having an average particle size of 80 μm with thecomposition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having anaverage particle size of 80 μm with the composition of Cr-25% Co-25%W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particlesize of 30 μm and a C powder having an average particle size of 18 μmwere prepared. These raw powders were blended according to theformulation shown in Table 16-1, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in a vacuum atmosphere at 0.1 Pa under theconditions of a temperature of 1150° C. and a retention time of 60minutes to obtain an iron-based sintered alloy 142 of the presentinvention, comparative sintered alloys 31 to 32, and a conventionalsintered alloy 44 shown in Table 16-2.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 142of the present invention, the comparative sintered alloys 31 to 32, andthe conventional sintered alloy 44 were produced and these cylindricalsintered alloy blocks for piercing test were repeatedly pierced untilthe drill is damaged, using a high-speed steel drill having a diameterof 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 16-2.    Machinability was evaluated by the results.

TABLE 16-1 Component ratio of raw powder (mass %) CaCO₃ powder Averageparticle size is Co-based Cr-based Fe-based Iron-based sintereddescribed in Mo alloy alloy Ni C Co alloy Fe alloy parenthesis. powderpowder# powder# powder powder powder powder# powder Product of the 142 0.5 (0.6 μm) 9.0 10 12 3 0.8 3.3 10 balance present inventionComparative 31 0.02* (40 μm*) 9.0 10 12 3 0.8 3.3 10 balance products 32 3.5* (0.01 μm*) 9.0 10 12 3 0.8 3.3 10 balance Conventional 44 CaF₂: 19.0 10 12 3 0.8 3.3 10 balance product Fe-based alloy powder#: Fe-13%Cr-5% Nb-0.8% Si Co-based alloy powder#: Co-30% Mo-10% Cr-3% Si Cr-basedalloy powder#: Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C The symbol *means the value which is not within the scope of the present invention.

TABLE 16-2 Component ratio of iron-based sintered alloy (mass %) Numberof Fe and inevitable piercing Iron-based sintered alloy CaCO₃ C Cr Mo WNi Si Co Nb impurities (times) Remarks Product of the present 142 0.47 16 12 3 3 0.5 11.7 1.1 balance 250 — invention Comparative products 310.01* 1 6 12 3 3 0.5 11.7 1.1 balance 14 — 32 3.47* 1 6 12 3 3 0.5 11.71.1 balance 140 decrease in strength Conventional 44 CaF₂: 1 1 6 12 3 30.5 11.7 1.1 balance 31 — product The symbol * means the value which isnot within the scope of the present invention.

As is apparent from the results shown in Table 16-1 and Table 16-2, thenumber of piercing of the cylindrical sintered alloy block for piercingtest made of the sintered alloy 142 of the present invention is largerthan that of the cylindrical sintered alloy block for piercing test madeof the conventional sintered alloy 44 and therefore the sintered alloyof the present invention is excellent in machinability. However, thecomparative sintered alloy 31 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 32 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 17

As raw powders, a CaCO₃ powder having an average particle size of 0.6μm, a CaF₂ powder having an average particle size of 36 μm, a Fe-basedalloy powder having an average particle size of 80 μm with thecomposition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having an averageparticle size of 80 μm, a Ni powder having an average particle size of 3μm, a Mo powder having an average particle size of 3 μm, a Co-basedalloy powder having an average particle size of 80 μm with thecomposition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having anaverage particle size of 80 μm with the composition of Cr-25% Co-25%W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particlesize of 30 μm and a C powder having an average particle size of 18 μmwere prepared. These raw powders were blended according to theformulation shown in Table 17-1, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in a vacuum atmosphere at 0.1 Pa under theconditions of a temperature of 1150° C. and a retention time of 60minutes and subjected to 18% Cu infiltration to obtain an iron-basedsintered alloy 143 of the present invention, comparative sintered alloys33 to 34, and a conventional sintered alloy 45 shown in Table 17-2.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 143of the present invention, the comparative sintered alloys 33 to 34, andthe conventional sintered alloy 45 were produced and these cylindricalsintered alloy blocks for piercing test were repeatedly pierced untilthe drill is damaged, using a high-speed steel drill having a diameterof 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 17-2.    Machinability was evaluated by the results.

TABLE 17-1 Component ratio of raw powder (mass %) CaCO₃ powder Co-Average particle size based Cr-based Fe-based Iron-based sintered isdescribed in Mo alloy alloy Ni C Co alloy Fe alloy parenthesis. powderpowder# powder# powder powder powder powder# Infiltration Cu powderProduct of the 143  0.5 (0.6 μm) 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18 balancepresent invention Comparative 33 0.02* (40 μm*) 1.5 5.0 19.0 3.0 1.5 4.49.0 18 balance products 34  3.5* (0.01 μm*) 1.5 5.0 19.0 3.0 1.5 4.4 9.018 balance Conventional 45 CaF₂: 1 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18balance product Fe-based alloy powder#: Fe-13% Cr-5% Nb-0.8% Si Co-basedalloy powder#: Co-30% Mo-10% Cr-3% Si Cr-based alloy powder#: Cr-25%Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C The symbol * means the value whichis not within the scope of the present invention.

TABLE 17-2 Component ratio of iron-based sintered alloy (mass %) Numberof Iron-based sintered Fe and inevitable piercing alloy CaCO₃ C Cr Mo WNi Si Co Nb Cu impurities (times) Remarks Product of the present 1430.47 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 346 — invention Comparativeproducts 33 0.01* 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 38 — 34 3.47* 1.88 3 4.8 5 0.4 12 1.1 18 balance 205 decrease in strength Conventionalproduct 45 CaF₂: 1 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 50 — The symbol *means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 17-1 and Table 17-2, thenumber of piercing of the cylindrical sintered alloy block for piercingtest made of the sintered alloy 143 of the present invention is largerthan that of the cylindrical sintered alloy block for piercing test madeof the conventional sintered alloy 45 and therefore the sintered alloyof the present invention is excellent in machinability. However, thecomparative sintered alloy 33 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 34 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 18

As raw powders, a CaCO₃ powder having an average particle size of 0.6μm, a CaF₂ powder having an average particle size of 36 μm, a Fe powderhaving an average particle size of 80 μm, a Ni powder having an averageparticle size of 3 μm, a Mo powder having an average particle size of 3μm, a Co powder having an average particle size of 30 μm and a C powderhaving an average particle size of 18 μm were prepared. These rawpowders were blended according to the formulation shown in Table 18-1,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in a vacuum atmosphereat 0.1 Pa under the conditions of a temperature of 1150° C. and aretention time of 60 minutes to obtain an iron-based sintered alloy 144of the present invention, comparative sintered alloys 35 to 36, and aconventional sintered alloy 46 shown in Table 18-2.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 144of the present invention, the comparative sintered alloys 35 to 36, andthe conventional sintered alloy 46 were produced and these cylindricalsintered alloy blocks for piercing test were repeatedly pierced untilthe drill is damaged, using a high-speed steel drill having a diameterof 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 18-2.    Machinability was evaluated by the results.

TABLE 18-1 Component ratio of raw powder (mass %) CaCO₃ powder Averageparticle size is Iron-based sintered alloy described in parenthesis. Mopowder Ni powder C powder Co powder Fe powder Product of the present 144 0.5 (0.6 μm) 2.0 2.0 1.3 1.0 balance invention Comparative products 350.02* (40 μm*) 2.0 2.0 1.3 1.0 balance 36  3.5* (0.01 μm*) 2.0 2.0 1.31.0 balance Conventional product 46 CaF₂: 1 2.0 2.0 1.3 1.0 balance Thesymbol * means the value which is not within the scope of the presentinvention.

TABLE 18-2 Component ratio of iron-based Number sintered alloy (mass %)of Fe and inevitable piercing Iron-based sintered alloy CaCO₃ C Mo Ni Coimpurities (times) Remarks Product 144 0.46 1.3 2 2 1 balance 287 — ofthe present invention Comparative products 35 0.01* 1.3 2 2 1 balance 27— 36 3.43* 1.3 2 2 1 balance 167 decrease in strength Conventionalproduct 46 CaF₂: 1 1.3 2 2 1 balance 37 — The symbol * means the valuewhich is not within the scope of the present invention.

As is apparent from the results shown in Table 18-1 and Table 18-2, thenumber of piercing of the cylindrical sintered alloy block for piercingtest made of the sintered alloy 144 of the present invention is largerthan that of the cylindrical sintered alloy block for piercing test madeof the conventional sintered alloy 46 and therefore the sintered alloyof the present invention is excellent in machinability. However, thecomparative sintered alloy 35 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 36 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 19

As raw powders, a CaCO₃ powder having an average particle size of 0.6μm, a CaF₂ powder having an average particle size of 36 μm and a SUS316(Fe-17% Cr-12% Ni-2.5% Mo) powder having an average particle size of 80μm were prepared. These raw powders were blended according to theformulation shown in Table 19, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in a vacuum atmosphere at 0.1 Pa under theconditions of a temperature of 1200° C. and a retention time of 60minutes to obtain an iron-based sintered alloy 145 of the presentinvention, comparative sintered alloys 37 to 38, and a conventionalsintered alloy 47.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 145of the present invention, the comparative sintered alloys 37 to 38, andthe conventional sintered alloy 47 were produced and these cylindricalsintered alloy blocks for piercing test were repeatedly pierced untilthe drill is damaged, using a high-speed steel drill having a diameterof 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 19.    Machinability was evaluated by the results.

TABLE 19 Component ratio of raw powder (mass %) Component ratio ofSUS316 iron-based sintered alloy CaCO₃ powder (Fe-17% (mass %) Averageparticle size Cr-12% Fe and Number of is described in Ni-2.5% inevitablepiercing Iron-based sintered alloy parenthesis. Mo) powder CaCO₃ Cr NiMo impurities (times) Remarks Product of the 145  0.5 (0.6 μm) balance0.48 17.1 12.3 2.2 balance 175 — present invention Comparative 37 0.02*(40 μm*)   balance 0.01* 17.1 12.3 2.2 balance 6 — products 38  3.5*(0.01 μm*) balance 3.43* 17.1 12.3 2.2 balance 105 decrease in strengthConventional 47 CaF₂: 1 balance CaF₂: 1 17.1 12.3 2.2 balance 15 —product The symbol * means the value which is not within the scope ofthe present invention.

As is apparent from the results shown in Table 19, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 145 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 47 and therefore the sintered alloy of thepresent invention is excellent in machinability. However, thecomparative sintered alloy 37 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 38 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 20

As raw powders, a CaCO₃ powder having an average particle size of 0.6μm, a CaF₂ powder having an average particle size of 36 μm and a SUS430(Fe-17% Cr) powder having an average particle size of 80 μm wereprepared. These raw powders were blended according to the formulationshown in Table 20, mixed in a double corn mixer and compacted to obtaina green compact, and then the resulting green compact was sintered in avacuum atmosphere at 0.1 Pa under the conditions of a temperature of1200° C. and a retention time of 60 minutes to obtain an iron-basedsintered alloy 146 of the present invention, comparative sintered alloys39 to 40, and a conventional sintered alloy 48.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 146of the present invention, the comparative sintered alloys 39 to 40, andthe conventional sintered alloy 48 were produced and these cylindricalsintered alloy blocks for piercing test were repeatedly pierced untilthe drill is damaged, using a high-speed steel drill having a diameterof 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 20.    Machinability was evaluated by the results.

TABLE 20 Component ratio Component ratio of iron-based of raw powder(mass %) sintered alloy (mass %) CaCO₃ powder SUS430 Fe and Number ofAverage particle size is (Fe-17% inevitable piercing Iron-based sinteredalloy described in parenthesis. Cr) powder CaCO₃ Cr impurities (times)Remarks Product of the present 146  0.5 (0.6 μm) balance 0.45 16.7balance 193 invention Comparative products 39 0.02 (40 μm*) balance0.01* 16.7 balance 24 40   35* (0.01 μm*) balance 3.43* 16.7 balance 134decrease in strength Conventional product 48 CaF₂: 1 balance CaF₂: 116.7 balance 31 The symbol * means the value which is not within thescope of the present invention.

As is apparent from the results shown in Table 20, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 146 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 48 and therefore the sintered alloy of thepresent invention is excellent in machinability. However, thecomparative sintered alloy 39 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 40 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 21

As raw powders, a CaCO₃ powder having an average particle size of 0.6μm, a CaF₂ powder having an average particle size of 36 μm, a C powderhaving an average particle size of 18 μm and a SUS410 (Fe-13% Cr) powderhaving an average particle size of 80 μm were prepared. These rawpowders were blended according to the formulation shown in Table 21,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in a vacuum atmosphereat 0.1 Pa under the conditions of a temperature of 1200° C. and aretention time of 60 minutes to obtain an iron-based sintered alloy 147of the present invention, comparative sintered alloys 41 to 42, and aconventional sintered alloy 49.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 147of the present invention, the comparative sintered alloys 41 to 42, andthe conventional sintered alloy 49 were produced and these cylindricalsintered alloy blocks for piercing test were repeatedly pierced untilthe drill is damaged, using a high-speed steel drill having a diameterof 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 21.    Machinability was evaluated by the results.

TABLE 21 Component ratio of raw powder (mass %) Component ratio ofiron-based CaCO₃ powder sintered alloy (mass %) Average particle size isSUS410 Fe and Number of described in C (Fe-13% inevitable piercingIron-based sintered alloy parenthesis. powder Cr) powder CaCO₃ Cr Cimpurities (times) Remarks Product of the 147  0.5 (0.6 μm) 0.15 balance0.49 12.8 0.1 balance 157 — present invention Comparative 41 0.02* (40μm*) 0.15 balance 0.01* 12.8 0.1 balance 10 — products 42  3.5* (0.01μm*) 0.15 balance 3.47* 12.8 0.1 balance 115 decrease in strengthConventional 49 CaF₂: 1 0.15 balance CaF₂: 1 12.8 0.1 balance 18 —product The symbol * means the value which is not within the scope ofthe present invention.

As is apparent from the results shown in Table 21, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 147 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 49 and therefore the sintered alloy of thepresent invention is excellent in machinability. However, thecomparative sintered alloy 41 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 42 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 22

As raw powders, a CaCO₃ powder having an average particle size of 0.6μm, a CaF₂ powder having an average particle size of 36 μm and a SUS630(Fe-17% Cr-4% Ni-4% Cu-0.3% Nb) powder having an average particle sizeof 80 μm were prepared. These raw powders were blended according to theformulation shown in Table 22, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in a vacuum atmosphere at 0.1 Pa under theconditions of a temperature of 1200° C. and a retention time of 60minutes to obtain an iron-based sintered alloy 148 of the presentinvention, comparative sintered alloys 43 to 44, and a conventionalsintered alloy 50.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 148of the present invention, the comparative sintered alloys 43 to 44, andthe conventional sintered alloy 50 were produced and these cylindricalsintered alloy blocks for piercing test were repeatedly pierced untilthe drill is damaged, using a high-speed steel drill having a diameterof 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 22.    Machinability was evaluated by the results.

TABLE 22 Component ratio of raw powder (mass %) Component ratio ofiron-based sintered CaCO₃ powder alloy (mass %) Average particle size Feand Number of is described in #SUS630 inevitable piercing Iron-basedsintered alloy parenthesis. powder CaCO₃ Cr Ni Cu Nb impurities (times)Remarks Product of the present 148  0.5 (0.6 μm) balance 0.45 16.8 4.1 40.3 balance 143 — invention Comparative products 43 0.02* (40 μm*)balance 0.01* 16.8 4.1 4 0.3 balance 13 — 44  3.5* (0.01 μm*) balance3.43* 16.8 4.1 4 0.3 balance 108 decrease in strength Conventionalproduct 50 CaF₂: 1 balance CaF₂: 1 16.8 4.1 4 0.3 balance 16 — #SUS630(Fe-17% Cr-4% Ni-4% Cu-0.3% Nb) The symbol * means the value which isnot within the scope of the present invention.

As is apparent from the results shown in Table 22, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 148 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 50 and therefore the sintered alloy of thepresent invention is excellent in machinability. However, thecomparative sintered alloy 43 containing CaCO₃ in the content of lessthan the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 44 containing CaCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 23

As raw powders, a SrCO₃ powder having an average particle size shown inTable 23 and a pure Fe powder having an average particle size of 80 μmwere prepared. These raw powders were blended according to theformulation shown in Table 23, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in an endothermic gas (ratio of components=H₂:40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere underthe conditions of a temperature of 1120° C. and a retention time of 20minutes to obtain iron-based sintered alloys 149 to 158 of the presentinvention and comparative sintered alloys 45 to 46.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 149to 158 of the present invention and the comparative sintered alloys 45to 46 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.030 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 23.    Machinability was evaluated by the results.

TABLE 23 Component ratio of Component ratio iron-based sintered of rawpowder (mass %) alloy (mass %) SrCO₃ powder Fe and Number of Averageparticle size is inevitable piercing Iron-based sintered alloy describedin parenthesis. Fe powder SrCO₃ impurities (times) Remarks Products ofthe 149  0.05 (0.1 μm) balance 0.05 balance 63 — present invention 150 0.2 (0.5 μm) balance 0.19 balance 130 — 151  0.5 (1 μm) balance 0.49balance 145 — 152  1.0 (1 μm) balance 0.98 balance 212 — 153  1.3 (0.5μm) balance 1.28 balance 190 — 154  1.5 (2 μm) balance 1.49 balance 245— 155  1.8 (18 μm) balance 1.80 balance 197 — 156  2.1 (2 μm) balance2.09 balance 188 — 157  2.5 (18 μm) balance 2.47 balance 219 — 158  3.0(30 μm) balance 2.99 balance 305 — Comparative 45 0.02* (40 μm*) balance0.01 balance 25 — products 46  3.5* (0.01 μm*) balance 3.47* balance 146decrease in strength The symbol * means the value which is not withinthe scope of the present invention.

As is apparent from the results shown in Table 23, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 149 to 158 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 1 to 3 shown in Table 1 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 45 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 46 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 24

As raw powders, a SrCO₃ powder having an average particle size shown inTable 24 and a Fe-0.6 mass % P powder having an average particle size of80 μm were prepared. These raw powders were blended according to theformulation shown in Table 24, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in an endothermic gas (ratio of components=H₂:40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere underthe conditions of a temperature of 1120° C. and a retention time of 20minutes to obtain iron-based sintered alloys 159 to 168 of the presentinvention and comparative sintered alloys 47 to 48.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 159to 168 of the present invention and the comparative sintered alloys 47to 48 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.030 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 24.    Machinability was evaluated by the results.

TABLE 24 Component ratio of raw powder Component ratio (mass %) ofiron-based SrCO₃ powder sintered alloy (mass %) Average particle size isFe-based Fe and Number of described in alloy inevitable piercingIron-based sintered alloy parenthesis. powder# SrCO₃ P impurities(times) Remarks Products of the 159  0.05 (0.1 μm) balance 0.04 0.55balance 51 — present invention 160  0.2 (0.5 μm) balance 0.18 0.58balance 121 — 161  0.5 (1 μm) balance 0.49 0.53 balance 167 — 162  1.0(1.0 μm) balance 0.99 0.53 balance 169 — 163  1.3 (0.5 μm) balance 1.280.57 balance 148 — 184  1.5 (2 μm) balance 1.48 0.57 balance 178 — 165 1.8 (18 μm) balance 1.79 0.54 balance 159 — 166  2.1 (2 μm) balance2.07 0.53 balance 110 — 167  2.5 (18 μm) balance 2.49 0.55 balance 135 —168  3.0 (30 μm) balance 2.99 0.55 balance 178 — Comparative 47 0.02*(40 μm*) balance 0.02* 0.56 balance 28 — products 48  3.5* (0.01 μm*)balance 3.48* 0.54 balance 163 decrease in strength The symbol * meansthe value which is not within the scope of the present invention.#Fe-based alloy powder with the composition of Fe-0.6 mass % P

As is apparent from the results shown in Table 24, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 159 to 168 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 4 to 6 shown in Table 2 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 47 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 48 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 25

As raw powders, a SrCO₃ powder having an average particle size shown inTable 25, a Fe powder having an average particle size of 80 μm and a Cpowder having an average particle size of 18 μm were prepared. These rawpowders were blended according to the formulation shown in Table 25,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in an endothermic gas(ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂:39.1%) atmosphere under the conditions of a temperature of 1120° C. anda retention time of 20 minutes to obtain iron-based sintered alloys 169to 178 of the present invention and comparative sintered alloys 49 to50.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 169to 178 of the present invention and the comparative sintered alloys 49to 50 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.018 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 25.    Machinability was evaluated by the results.

TABLE 25 Component ratio of raw powder (mass %) Component ratio ofiron-based SrCO₃ powder sintered alloy (mass %) Average particle Fe andNumber of Iron-based sintered size is described C Fe inevitable piercingalloy in parenthesis. powder powder Infiltration Cu SrCO₃ C Cuimpurities (times) Remarks Products of 169  0.05 (0.1 μm) 0.13 balance20 0.05 0.12 19.5 balance 83 — the present 170  0.2 (0.5 μm) 0.3 balance20 0.20 0.24 20.2 balance 130 — invention 171  0.5 (1 μm) 0.6 balance 200.49 0.54 20.1 balance 175 — 172  1.0 (2 μm) 0.8 balance 20 0.97 0.7519.6 balance 203 — 173  1.3 (0.5 μm) 1.1 balance 20 1.28 1.05 19.9balance 182 — 174  1.6 (2 μm) 1.1 balance 20 1.46 0.99 20.4 balance 192— 175  1.8 (18 μm) 1.1 balance 20 1.77 1.05 19.8 balance 183 — 176  2.1(2 μm) 1.1 balance 20 2.09 1.07 20.0 balance 209 — 177  2.5 (18 μm) 1.1balance 20 2.45 1.07 19.7 balance 197 — 178  3.0 (30 μm) 1.2 balance 202.96 1.15 19.9 balance 172 — Comparative 49 0.02* (40 μm*) 1.1 balance20 0.01* 1.04 20.3 balance 25 — products 50  3.5* (0.01 μm*) 1.1 balance20 3.45* 1.06 19.6 balance 124 decrease in strength The symbol * meansthe value which is not within the scope of the present invention.

As is apparent from the results shown in Table 25, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 169 to 178 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 7 to 9 shown in Table 3 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 49 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 50 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 26

As raw powders, a SrCO₃ powder having an average particle size shown inTable 26, a Fe powder having an average particle size of 80 μm and a Cpowder having an average particle size of 18 μm were prepared. These rawpowders were blended according to the formulation shown in Table 26,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in an endothermic gas(ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂:39.1%) atmosphere under the conditions of a temperature of 1120° C. anda retention time of 20 minutes and subjected to 20% Cu infiltration toobtain iron-based sintered alloys 179 to 188 of the present inventionand comparative sintered alloys 51 to 52.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 179to 188 of the present invention and the comparative sintered alloys 51to 52 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.018 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 26.    Machinability was evaluated by the results.

TABLE 26 Component ratio Component ratio of raw powder (mass %) ofiron-based sintered SrCO₃ powder alloy (mass %) Average particle size Feand Number of Iron-based sintered is described in C inevitable piercingalloy parenthesis. powder Fe powder SrCO₃ C impurities (times) RemarksProducts of the 179 0.05 (0.1 μm) 0.13 balance 0.05 0.12 balance 75 —present 180  0.2 (0.5 μm) 0.3 balance 0.20 0.24 balance 110 — invention181  0.5 (1 μm) 0.6 balance 0.49 0.54 balance 156 — 182  1.0 (2 μm) 0.8balance 0.97 0.75 balance 172 — 183  1.3 (0.5 μm) 1.1 balance 1.28 1.05balance 181 — 184  1.5 (2 μm) 1.1 balance 1.46 0.99 balance 205 — 185 1.8 (18 μm) 1.1 balance 1.77 1.05 balance 171 — 186  2.1 (2 μm) 1.1balance 2.09 1.07 balance 220 — 187  2.5 (18 μm) 1.1 balance 2.45 1.07balance 199 — 188  3.0 (30 μm) 1.2 balance 2.96 1.15 balance 194 —Comparative 51 0.02* (40 μm*) 1.1 balance 0.01* 1.04 balance 15 —products 52  3.5* (0.01 μm*) 1.1 balance 3.45* 1.06 balance 122 decreasein strength The symbol * means the value which is not within the scopeof the present invention.

As is apparent from the results shown in Table 26, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 179 to 188 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 10 to 12 shown in Table 4 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 51 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 52 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 27

As raw powders, a SrCO₃ powder having an average particle size shown inTable 27, a Fe powder having an average particle size of 80 μm, a Cupowder having an average particle size of 25 μm and a C powder having anaverage particle size of 18 μm were prepared. These raw powders wereblended according to the formulation shown in Table 27, mixed in adouble corn mixer and compacted to obtain a green compact, and then theresulting green compact was sintered in an endothermic gas (ratio ofcomponents=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%)atmosphere under the conditions of a temperature of 1120° C. and aretention time of 20 minutes to obtain iron-based sintered alloys 189 to198 of the present invention and comparative sintered alloys 53 to 54.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 189to 198 of the present invention and the comparative sintered alloys 53to 54 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.030 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 27.    Machinability was evaluated by the results.

TABLE 27 Component ratio of raw powder (mass %) Component ratio ofiron-based SrCO₃ powder sintered alloy (mass %) Average particle size Feand Number of Iron-based sintered is described in Cu C Fe inevitablepiercing alloy parenthesis. powder powder powder SrCO₃ Cu C impurities(times) Remarks Products of the 189  0.05 (0.1 μm) 0.2 0.13 balance 0.032.0 0.11 balance 48 — present 190  0.2 (0.5 μm) 2 0.25 balance 0.18 2.10.22 balance 127 — invention 191  0.5 (1 μm) 2 0.98 balance 0.48 1.90.87 balance 136 — 192  1.0 (2 μm) 2 0.7 balance 0.96 2.0 0.68 balance225 — 193  1.3 (0.5 μm) 2 0.7 balance 1.25 2.0 0.64 balance 247 — 194 1.5 (2 μm) 4 0.7 balance 1.46 4.0 0.65 balance 229 — 195  1.8 (18 μm)5.8 0.7 balance 1.77 5.7 0.67 balance 213 — 196  2.1 (2 μm) 4 0.7balance 2.09 3.9 0.64 balance 200 — 197  2.5 (18 μm) 2 0.98 balance 2.482.0 0.92 balance 179 — 198  3.0 (30 μm) 2 1.2 balance 2.97 2.0 1.16balance 154 — Comparative 53 0.02* (40 μm*) 2 0.7 balance 0.01* 1.9 0.67balance 8 — products 54  3.5* (0.01 μm*) 2 0.7 balance 3.47* 2.0 0.65balance 148 decrease in strength The symbol * means the value which isnot within the scope of the present invention.

As is apparent from the results shown in Table 27, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 189 to 198 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 13 to 15 shown in Table 5 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 53 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 54 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 28

As raw powders, a SrCO₃ powder having an average particle size shown inTable 28, a partially diffused Fe-based alloy powder having an averageparticle size of 80 μm with the composition of Fe-1.5% Cu-4.0% Ni-0.5%Mo and a C powder having an average particle size of 18 μm wereprepared. These raw powders were blended according to the formulationshown in Table 28, mixed in a double corn mixer and compacted to obtaina green compact, and then the resulting green compact was sintered in anendothermic gas (ratio of components=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%,CH: 0.5%, and N₂: 39.1%) atmosphere under the conditions of atemperature of 1120° C. and a retention time of 20 minutes to obtainiron-based sintered alloys 199 to 208 of the present invention andcomparative sintered alloys 55 to 56.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 199to 208 of the present invention and the comparative sintered alloys 55to 56 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 28.    Machinability was evaluated by the results.

TABLE 28 Component ratio of raw powder (mass %) Component ratio ofiron-based sintered alloy SrCO₃ powder (mass %) Average particleFe-based Fe and Number of Iron-based sintered size is described in Calloy inevitable piercing alloy parenthesis. powder powder# SrCO₃ Cu CNi Mo impurities (times) Remarks Products of the 199  0.05 (0.1 μm) 0.13balance 0.03 1.5 0.11 3.9 0.50 balance 51 — present 200  0.2 (0.5 μm)0.25 balance 0.18 1.5 0.19 4.0 0.50 balance 148 — invention 201  0.5 (1μm) 0.98 balance 0.46 1.5 0.85 4.0 0.50 balance 208 — 202  1.0 (2 μm)0.5 balance 0.96 1.4 0.47 4.1 0.52 balance 308 — 203  1.3 (0.5 μm) 0.5balance 1.25 1.5 0.45 4.0 0.50 balance 301 — 204  1.5 (2 μm) 0.5 balance1.45 1.5 0.45 4.0 0.50 balance 315 — 205  1.8 (18 μm) 0.5 balance 1.721.5 0.47 4.0 0.49 balance 268 — 206  2.1 (2 μm) 0.5 balance 2.05 1.60.47 3.8 0.50 balance 298 — 207  2.5 (18 μm) 1.0 balance 2.44 1.5 0.904.0 0.50 balance 286 — 208  3.0 (30 μm) 1.2 balance 2.93 1.5 1.17 4.00.50 balance 248 — Comparative 55 0.02* (40 μm*) 0.5 balance 0.01* 1.50.43 4.1 0.50 balance 9 — products 56  3.5* (0.01 μm*) 0.5 balance 3.42*1.5 0.44 4.0 0.51 balance 130 decrease in strength The symbol * meansthe value which is not within the scope of the present invention.#partially diffused Fe-based alloy powder having an average particlesize of 80 μm with the composition of Fe-1.5% Cu-4.0% Ni-0.5% Mo

As is apparent from the results shown in Table 28, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 199 to 208 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 16 to 18 shown in Table 6 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 55 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 56 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 29

As raw powders, a SrCO₃ powder having an average particle size shown inTable 29, a Fe-based alloy powder having an average particle size of 80μm with the composition of Fe-1.5% Mo and a C powder having an averageparticle size of 18 μm were prepared. These raw powders were blendedaccording to the formulation shown in Table 29, mixed in a double cornmixer and compacted to obtain a green compact, and then the resultinggreen compact was sintered in an endothermic gas (ratio ofcomponents=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%)atmosphere under the conditions of a temperature of 1120° C. and aretention time of 20 minutes to obtain iron-based sintered alloys 209 to218 of the present invention and comparative sintered alloys 57 to 58.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 209to 218 of the present invention and the comparative sintered alloys 57to 58 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 29.    Machinability was evaluated by the results.

TABLE 29 Component ratio of raw powder (mass %) Component ratio ofiron-based SrCO₃ powder sintered alloy (mass %) Average particle sizeFe-based Fe and Number of Iron-based sintered is described in C alloyinevitable piercing alloy parenthesis. powder powder# SrCO₃ C Moimpurities (times) Remarks Products of the 209  0.05 (0.1 μm) 0.13balance 0.04 0.11 1.48 balance 55 — present 210  0.2 (0.5 μm) 0.25balance 0.18 0.19 1.48 balance 89 — invention 211  0.5 (1 μm) 0.98balance 0.48 0.88 1.50 balance 83 — 212  1.0 (2 μm) 0.5 balance 0.980.45 1.51 balance 187 — 213  1.3 (0.5 μm) 0.5 balance 1.25 0.44 1.50balance 214 — 214  1.5 (2 μm) 0.5 balance 1.46 0.47 1.51 balance 235 —215  1.8 (18 μm) 0.5 balance 1.73 0.43 1.46 balance 210 — 216  2.1 (2μm) 0.5 balance 2.01 0.48 1.48 balance 222 — 217  2.5 (18 μm) 1.0balance 2.45 0.96 1.50 balance 156 — 218  3.0 (30 μm) 1.2 balance 2.931.13 1.48 balance 169 — Comparative 57 0.02* (40 μm*) 0.5 balance 0.01*0.45 1.50 balance 18 — products 58  3.5* (0.01 μm*) 0.5 balance 3.47*0.46 1.50 balance 106 decrease in strength The symbol * means the valuewhich is not within the scope of the present invention. #Fe-based alloypowder having a particle size of 80 μm with the composition of Fe-1.5%Mo

As is apparent from the results shown in Table 29, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 209 to 218 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 19 to 21 shown in Table 7 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 57 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 58 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 30

As raw powders, a SrCO₃ powder having an average particle size shown inTable 30, a Fe-based alloy powder having an average particle size of 80μm with the composition of Fe-3.0% Cr-0.5% Mo and a C powder having anaverage particle size of 18 μm were prepared. These raw powders wereblended according to the formulation shown in Table 30, mixed in adouble corn mixer and compacted to obtain a green compact, and then theresulting green compact was sintered in an N₂+5% H₂ gas mixture underthe conditions of a temperature of 1120° C. and a retention time of 20minutes to obtain iron-based sintered alloys 219 to 228 of the presentinvention and comparative sintered alloys 59 to 60.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 219to 228 of the present invention and the comparative sintered alloys 59to 60 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 30.    Machinability was evaluated by the results.

TABLE 30 Component ratio of raw powder (mass %) Component ratio ofiron-based sintered SrCO₃ powder alloy (mass %) Average particle sizeFe-based Fe and Number of Iron-based is described in C alloy inevitablepiercing sintered alloy parenthesis. powder powder# SrCO₃ C Cr Moimpurities (times) Remarks Products of the 219  0.05 (0.1 μm) 0.13balance 0.03 0.11 3.0 0.50 balance 56 — present 220  0.2 (0.5 μm) 0.25balance 0.19 0.19 3.0 0.50 balance 87 — invention 221  0.5 (1 μm) 0.98balance 0.48 0.85 3.0 0.51 balance 98 — 222  1.0 (2 μm) 0.5 balance 0.970.47 3.0 0.50 balance 150 — 223  1.3 (0.5 μm) 0.5 balance 1.27 0.45 2.90.50 balance 203 — 224  1.5 (2 μm) 0.5 balance 1.44 0.45 3.0 0.51balance 211 — 225  1.8 (18 μm) 0.5 balance 1.72 0.44 3.0 0.49 balance175 — 226  2.1 (2 μm) 0.5 balance 1.95 0.44 3.1 0.48 balance 188 — 227 2.5 (18 μm) 1.0 balance 2.39 0.90 3.0 0.50 balance 142 — 228  3.0 (30μm) 1.2 Balance 2.91 1.17 3.0 0.50 balance 111 — Comparative 59 0.02*(40 μm*) 0.5 balance 0.01* 0.43 3.1 0.50 balance 2 — products 60  3.5*(0.01 μm*) 0.5 balance 3.45* 0.45 3.0 0.50 balance 98 decrease instrength The symbol * means the value which is not within the scope ofthe present invention. #Fe-based alloy powder having a particle size of:80 μm with the composition of Fe-3.0% Cr-0.5% Mo

As is apparent from the results shown in Table 30, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 219 to 228 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 22 to 24 shown in Table 8 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 59 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 60 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 31

As raw powders, a SrCO₃ powder having an average particle size shown inTable 31, a Fe-based alloy powder having an average particle size of 80μm with the composition of Fe-3.0% Cr-0.5% Mo, a Ni powder having anaverage particle size of 3 μm and a C powder having an average particlesize of 18 μm were prepared. These raw powders were blended according tothe formulation shown in Table 31, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in an N₂+5% H₂ gas mixture under the conditions ofa temperature of 1120° C. and a retention time of 20 minutes to obtainiron-based sintered alloys 229 to 238 of the present invention andcomparative sintered alloys 61 to 62.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 229to 238 of the present invention and the comparative sintered alloys 61to 62 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 31.    Machinability was evaluated by the results.

TABLE 31 Component ratio of raw powder (mass %) Component ratio ofiron-based sintered alloy SrCO₃ powder (mass %) Number Average particleFe-based Fe and of Iron-based size is described C Ni alloy inevitablepiercing sintered alloy in parenthesis. powder powder powder# SrCO₃ C NiCr Mo impurities (times) Remarks Products of 229  0.05 (0.1 μm) 0.13 0.2balance 0.03 0.11 0.2 3.0 0.50 balance 57 — the present 230  0.2 (0.5μm) 0.25 2 balance 0.19 0.19 1.9 2.8 0.50 balance 100 — invention 231 0.5 (1 μm) 0.98 4 balance 0.48 0.85 4.1 3.0 0.49 balance 125 — 232  1.0(2 μm) 0.5 4 balance 0.97 0.47 4.0 3.0 0.50 balance 184 — 233  1.3 (0.5μm) 0.5 4 balance 1.27 0.45 4.0 2.9 0.50 balance 122 — 234  1.5 (2 μm)0.5 4 balance 1.44 0.45 4.0 3.0 0.49 balance 145 — 235  1.8 (18 μm) 0.54 balance 1.72 0.44 3.9 2.9 0.49 balance 144 — 236  2.1 (2 μm) 0.5 6balance 1.95 0.44 6.0 3.0 0.50 balance 135 — 237  2.5 (18 μm) 1.0 8balance 2.39 0.90 7.9 3.0 0.50 balance 126 — 238  3.0 (30 μm) 1.2 9.8balance 2.91 1.17 9.8 3.0 0.50 balance 108 — Comparative 61 0.02* (40μm*) 0.5 4 balance 0.01* 0.43 4.0 3.0 0.50 balance 5 — products 62  3.5*(0.01 μm*) 0.5 4 balance 3.45* 0.45 4.0 3.0 0.50 balance 120 decrease instrength The symbol * means the value which is not within the scope ofthe present invention. #Fe-based alloy powder having a particle size of:80 μm with the composition of Fe-3.0% Cr-0.5% Mo

As is apparent from the results shown in Table 31, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 229 to 238 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 25 to 27 shown in Table 9 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 61 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 62 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 32

As raw powders, a SrCO₃ powder having an average particle size shown inTable 32, a Fe-based alloy powder having an average particle size of 80μm with the composition of Fe-3.0% Cr-0.5% Mo, a Cu powder having anaverage particle size of 25 μm, a Ni powder having an average particlesize of 3 μm and a C powder having an average particle size of 18 μmwere prepared. These raw powders were blended according to theformulation shown in Table 32, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in an N₂+5% H₂ gas mixture under the conditions ofa temperature of 1120° C. and a retention time of 20 minutes to obtainiron-based sintered alloys 239 to 248 of the present invention andcomparative sintered alloys 63 to 64.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 239to 248 of the present invention and the comparative sintered alloys 63to 64 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 32.    Machinability was evaluated by the results.

TABLE 32 Component ratio of raw powder (mass %) SrCO₃ powder Componentratio of iron-based Average sintered alloy (mass %) Number particle sizeis Fe-based Fe and of Iron-based described in Cu C Ni alloy inevitablepiercing sintered alloy parenthesis. powder powder powder powder# SrCO₃Cu C Ni Cr Mo impurities (times) Remarks Products 239  0.05 (0.1 μm) 0.20.13 0.2 balance 0.03 0.2 0.11 0.2 3.0 0.50 balance 31 — of the 240  0.2(0.5 μm) 2 0.25 2 balance 0.19 2.1 0.22 2.0 3.0 0.50 balance 95 —present 241  0.5 (1 μm) 2 0.98 4 balance 0.48 1.9 0.92 4.0 3.0 0.49balance 108 — invention 242  1.0 (2 μm) 2 0.5 4 balance 0.97 2.0 0.474.0 3.1 0.51 balance 145 — 243  1.3 (0.5 μm) 2 0.5 4 balance 1.27 2.00.47 3.9 2.9 0.50 balance 149 — 244  1.5 (2 μm) 4 0.5 4 balance 1.44 4.00.45 4.0 3.0 0.50 balance 143 — 245  1.8 (18 μm) 5.8 0.5 4 balance 1.775.8 0.45 4.0 3.0 0.49 balance 136 — 246  2.1 (2 μm) 4 0.5 6 balance 2.044.0 0.44 6.0 3.0 0.50 balance 151 — 247  2.5 (18 μm) 2 1.0 8 balance2.42 2.0 0.94 7.9 3.0 0.50 balance 140 — 248  3.0 (30 μm) 2 1.2 9.8balance 2.96 2.0 1.15 9.8 3.0 0.50 balance 121 — Compara- 63 0.02* (40μm*) 2 0.5 4 balance 0.01* 1.9 0.46 4.1 3.0 0.50 balance 3 — tive 64 3.5* (0.01 μm*) 2 0.5 4 balance 3.46* 2.0 0.45 4.0 3.0 0.50 balance 125decrease products in strength The symbol * means the value which is notwithin the scope of the present invention. #Fe-based alloy powder havinga particle size of 80 μm with the composition of Fe-3.0% Cr-0.5% Mo

As is apparent from the results shown in Table 32, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 239 to 248 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 28 to 30 shown in Table 10 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 63 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 64 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 33

As raw powders, a SrCO₃ powder having an average particle size shown inTable 33, a Fe powder having an average particle size of 80 μm, a Nipowder having an average particle size of 3 μm and a C powder having anaverage particle size of 18 μm were prepared. These raw powders wereblended according to the formulation shown in Table 33, mixed in adouble corn mixer and compacted to obtain a green compact, and then theresulting green compact was sintered in an endothermic gas (ratio ofcomponents=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%)atmosphere under the conditions of a temperature of 1120° C. and aretention time of 20 minutes to obtain iron-based sintered alloys 249 to258 of the present invention and comparative sintered alloys 65 to 66.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 249to 258 of the present invention and the comparative sintered alloys 65to 66 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.009 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 33.    Machinability was evaluated by the results.

TABLE 33 Component ratio of raw powder (mass %) Component ratio ofiron-based SrCO₃ powder sintered alloy (mass %) Average particle size Feand Number of Iron-based sintered is described in C Ni Fe inevitablepiercing alloy parenthesis. powder powder powder SrCO₃ C Ni impurities(times) Remarks Products of the 249  0.05 (0.1 μm) 0.13 0.2 balance 0.040.12 0.2 balance 45 — present 250  0.2 (0.5 μm) 0.25 1 balance 0.24 0.231.0 balance 80 — invention 251  0.5 (1 μm) 0.98 3 balance 0.47 0.92 2.9balance 86 — 252  1.0 (2 μm) 0.5 3 balance 0.98 0.46 3.0 balance 202 —253  1.3 (0.5 μm) 0.5 3 balance 1.28 0.44 3.0 balance 136 — 254  1.5 (2μm) 0.5 3 balance 1.47 0.47 3.0 balance 187 — 255  1.8 (18 μm) 0.5 3balance 1.75 0.46 3.0 balance 196 — 256  2.1 (2 μm) 0.5 6 balance 2.060.45 6.0 balance 154 — 257  2.5 (18 μm) 1.0 8 balance 2.44 0.92 8.0balance 136 — 258  3.0 (30 μm) 1.2 9.8 balance 2.98 1.13 9.8 balance 95— Comparative 65 0.02* (40 μm*) 0.5 3 balance 0.01* 0.45 3.0 balance 5 —products 66  3.5* (0.01 μm*) 0.5 3 balance 3.49* 0.45 3.0 balance 137decrease in strength The symbol * means the value which is not withinthe scope of the present invention.

As is apparent from the results shown in Table 33, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 249 to 258 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 31 to 33 shown in Table 11 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 65 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 66 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 34

As raw powders, a SrCO₃ powder having an average particle size shown inTable 34, a Fe powder having an average particle size of 80 μm, a Nipowder having an average particle size of 3 μm, a Mo powder having anaverage particle size of 3 μm and a C powder having an average particlesize of 18 μm were prepared. These raw powders were blended according tothe formulation shown in Table 34, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in an endothermic gas (ratio of components=H₂:40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere underthe conditions of a temperature of 1120° C. and a retention time of 20minutes to obtain iron-based sintered alloys 259 to 268 of the presentinvention and comparative sintered alloys 67 to 68. Cylindrical sinteredalloy blocks for piercing test each having a diameter of 30 mm and aheight of 10 mm, made of the sintered alloys 259 to 268 of the presentinvention and the comparative sintered alloys 67 to 68 were produced andthese cylindrical sintered alloy blocks for piercing test wererepeatedly pierced until the drill is damaged, using a high-speed steeldrill having a diameter of 1.2 mm, under the following conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.009 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 34.    Machinability was evaluated by the results.

TABLE 34 Component ratio of raw powder (mass %) Component ratio ofiron-based SrCO₃ powder sintered alloy (mass %) Number Average particleFe and of Iron-based sintered size is described C Ni Mo Fe inevitablepiercing alloy in parenthesis. powder powder powder powder SrCO₃ C Ni Moimpurities (times) Remarks Products of 259  0.05 (0.1 μm) 0.13 0.2 0.2balance 0.05 0.11 0.2 0.2 balance 55 — the present 260  0.2 (0.5 μm)0.25 1 0.3 balance 0.19 0.18 1.0 0.3 balance 101 — invention 261  0.5 (1μm) 0.98 4 0.5 balance 0.44 0.93 4.0 0.5 balance 103 — 262  1.0 (2 μm)0.6 4 0.5 balance 0.98 0.55 4.0 0.5 balance 204 — 263  1.3 (0.5 μm) 0.64 0.5 balance 1.28 0.57 4.0 0.5 balance 214 — 264  1.5 (2 μm) 0.6 4 1balance 1.48 0.54 3.9 1.0 balance 187 — 265  1.8 (18 μm) 0.6 4 3 balance0.76 0.54 3.9 2.9 balance 169 — 266  2.1 (2 μm) 0.6 6 4.8 balance 1.940.54 6.0 4.7 balance 159 — 267  2.5 (18 μm) 1.0 8 0.5 balance 2.47 0.958.0 0.5 balance 128 — 268  3.0 (30 μm) 1.2 9.8 0.5 balance 2.95 1.14 9.80.5 balance 159 — Comparative 67 0.02* (40 μm*) 0.6 4 0.5 balance 0.01*0.54 4.0 0.5 balance 9 — products 68  3.5* (6.01 μm*) 0.6 4 0.5 balance3.46* 0.54 4.0 0.5 balance 106 decrease in strength The symbol * meansthe value which is not within the scope of the present invention.

As is apparent from the results shown in Table 34, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 259 to 268 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 34 to 36 shown in Table 12 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 67 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 68 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 35

As raw powders, a SrCO₃ powder having an average particle size shown inTable 35, a Fe powder having an average particle size of 80 μm, a Nipowder having an average particle size of 3 μm, a Cu powder having anaverage particle size of 25 μm and a C powder having an average particlesize of 18 μm were prepared. These raw powders were blended according tothe formulation shown in Table 35, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in an endothermic gas (ratio of components H₂:40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%) atmosphere underthe conditions of a temperature of 1120° C. and a retention time of 20minutes to obtain iron-based sintered alloys 269 to 278 of the presentinvention and comparative sintered alloys 69 to 70.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 269to 278 of the present invention and the comparative sintered alloys 69to 70 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.009 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 35.    Machinability was evaluated by the results.

TABLE 35 Component ratio of raw powder (mass %) Component ratio ofiron-based sintered SrCO₃ powder alloy (mass %) Average particle size Feand Number of Iron-based sintered is described in Cu C Ni Fe inevitablepiercing alloy parenthesis. powder powder powder powder SrCO₃ Cu C Niimpurities (times) Remarks Products of 269  0.05 (0.1 μm) 0.2 0.13 0.2balance 0.04 0.2 0.11 0.2 balance 49 — the present 270  0.2 (0.5 μm) 10.25 1 balance 0.19 1.0 0.21 1.0 balance 100 — invention 271  0.5 (1 μm)1 0.98 3 balance 0.45 1.0 0.95 3.0 balance 128 — 272  1.0 (2 μm) 1 0.6 3balance 0.96 0.99 0.55 3.0 balance 180 — 273  1.3 (0.5 μm) 2 0.6 3balance 1.27 1.0 0.54 3.0 balance 184 — 274  1.5 (2 μm) 4 0.6 3 balance1.48 4.0 0.55 2.9 balance 158 — 275  1.8 (18 μm) 5.8 0.6 3 balance 1.765.7 0.56 3.0 balance 179 — 276  2.1 (2 μm) 1 0.6 6 balance 1.95 1.0 0.556.0 balance 164 — 277  2.5 (18 μm) 1 1.0 8 balance 2.45 1.0 0.91 8.0balance 155 — 278  3.0 (30 μm) 1 1.2 9.8 balance 2.96 1.0 1.16 9.8balance 147 — Comparative 69 0.02* (40 μm*) 1 0.6 3 balance 0.01* 1.00.55 3.0 balance 10 — products 70  3.5* (0.01 μm*) 1 0.6 3 balance 3.44*1.0 0.55 3.0 balance 75 decrease in strength The symbol * means thevalue which is not within the scope of the present invention.

As is apparent from the results shown in Table 35, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 269 to 278 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 37 to 39 shown in Table 13 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 69 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 70 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred

EXAMPLE 36

As raw powders, a SrCO₃ powder having an average particle size shown inTable 36, a Fe powder having an average particle size of 80 μm, a Cu—Ppowder having an average particle size of 25 μm and a C powder having anaverage particle size of 18 μm were prepared. These raw powders wereblended according to the formulation shown in Table 36, mixed in adouble corn mixer and compacted to obtain a green compact, and then theresulting green compact was sintered in an endothermic gas (ratio ofcomponents=H₂: 40.5%, CO: 19.8%, CO₂: 0.1%, CH: 0.5%, and N₂: 39.1%)atmosphere under the conditions of a temperature of 1120° C. and aretention time of 20 minutes to obtain iron-based sintered alloys 279 to288 of the present invention and comparative sintered alloys 71 to 72.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloys 279to 288 of the present invention and the comparative sintered alloys 71to 72 were produced and these cylindrical sintered alloy blocks forpiercing test were repeatedly pierced until the drill is damaged, usinga high-speed steel drill having a diameter of 1.2 mm, under thefollowing conditions:

-   Rotating speed: 10000 rpm-   Feed speed: 0.009 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 36.    Machinability was evaluated by the results.

TABLE 36 Component ratio of raw powder (mass %) Component ratio ofiron-based SrCO₃ powder sintered alloy (mass %) Number Average particlesize Fe and of Iron-based sintered is described in C Cu-P Fe inevitablepiercing alloy parenthesis. powder powder powder SrCO₃ C Cu P impurities(times) Remarks Products of the 279  0.05 (0.1 μm) 1.0 0.7 balance 0.030.90 0.6 0.1 balance 71 — present 280  0.2 (0.5 μm) 1.5 1.2 balance 0.171.42 1.1 0.1 balance 88 — invention 281  0.5 (1 μm) 1.5 1.8 balance 0.461.45 1.6 0.2 balance 102 — 282  1.0 (2 μm) 2.0 1.8 balance 0.95 1.95 1.60.2 balance 199 — 283  1.3 (0.5 μm) 2.0 2.8 balance 1.25 1.94 2.5 0.3balance 240 — 284  1.5 (2 μm) 2.0 2.8 balance 1.44 1.93 2.5 0.3 balance209 — 285  1.8 (18 μm) 2.0 3.3 balance 1.73 1.94 3 0.3 balance 255 — 286 2.1 (2 μm) 2.5 6.0 balance 1.89 2.45 5.4 0.6 balance 190 — 287  2.5 (18μm) 2.5 8.0 balance 2.40 2.44 5 0.6 balance 202 — 288  3.0 (30 μm) 3.09.0 balance 2.92 2.97 8.2 0.8 balance 265 — Comparative 71 0.02* (40μm*) 1 2.8 balance 0.01* 0.44 2.5 0.3 balance 5 — products 72  3.5*(0.01 μm*) 1 2.8 balance 3.43* 0.45 2.5 0.3 balance 169 decrease instrength The symbol * means the value which is not within the scope ofthe present invention.

As is apparent from the results shown in Table 36, the number ofpiercing of the cylindrical sintered alloy blocks for piercing test madeof the sintered alloys 279 to 288 of the present invention is largerthan that of the cylindrical sintered alloy blocks for piercing testmade of the conventional sintered alloys 40 to 42 shown in Table 14 andtherefore the sintered alloys of the present invention are excellent inmachinability. However, the comparative sintered alloy 71 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 72 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 37

As raw powders, a SrCO₃ powder having an average particle size of 1 μmand a Fe-6% Cr-6% Mo-9% W-3% V-10% Co-1.5% C powder having an averageparticle size of 80 μm were prepared. These raw powders were blendedaccording to the formulation shown in Table 37, mixed in a double cornmixer and compacted to obtain a green compact, and then the resultinggreen compact was sintered in a dissociated ammonia gas atmosphere underthe conditions of a temperature of 1150° C. and a retention time of 60minutes to obtain an iron-based sintered alloy 289 of the presentinvention and comparative sintered alloys 73 to 74.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 289of the present invention and the comparative sintered alloys 73 to 74were produced and these cylindrical sintered alloy blocks for piercingtest were repeatedly pierced until the drill is damaged, using ahigh-speed steel drill having a diameter of 1.2 mm, under the followingconditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 37.    Machinability was evaluated by the results.

TABLE 37 Component ratio of raw powder (mass %) Fe-6% Cr- SrCO₃ powder6% Mo- Component ratio of iron-based sintered alloy Average 9% W-3% V-(mass %) particle size 10% Co- Fe and Number of Iron-based sintered isdescribed in 1.5% C inevitable piercing alloy parenthesis. powder SrCO₃C Cr Mo W Co V impurities (times) Remarks Product of the 289  0.5 (1 μm)balance 0.49 1.5 6 6 9 10 3 balance 150 — present invention Comparative73 0.02* (40 μm*) balance 0.01* 1.5 6 6 9 10 3 balance 16 — products 74 3.5* (0.01 μm*) balance 3.43* 1.5 6 6 9 10 3 balance 121 decrease instrength The symbol * means the value which is not within the scope ofthe present invention.

As is apparent from the results shown in Table 37, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 289 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 43 shown in Table 15 and therefore thesintered alloy of the present invention is excellent in machinability.However, the comparative sintered alloy 73 containing SrCO₃ in thecontent of less than the range defined in the present invention isinferior in machinability because of small number of piercing, while thecomparative sintered alloy 74 containing SrCO₃ in the content of morethan the range defined in the present invention is excellent inmachinability because of large number of piercing, but shows drasticallydecreased deflection strength, and therefore it is not preferred.

EXAMPLE 38

As raw powders, a SrCO₃ powder having an average particle size of 1 μm,a Fe-based alloy powder having an average particle size of 80 μm withthe composition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having anaverage particle size of 80 μm, a Ni powder having an average particlesize of 3 μm, a Mo powder having an average particle size of 3 μm, aCo-based alloy powder having an average particle size of 80 μm with thecomposition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having anaverage particle size of 80 μm with the composition of Cr-25% Co-25%W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particlesize of 30 μm and a C powder having an average particle size of 18 μmwere prepared. These raw powders were blended according to theformulation shown in Table 38-1, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in a vacuum atmosphere at 0.1 Pa under theconditions of a temperature of 1150° C. and a retention time of 60minutes to obtain an iron-based sintered alloy 290 of the presentinvention and comparative sintered alloys 75 to 76 shown in Table 38-2.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 290of the present invention and the comparative sintered alloys 75 to 76were produced and these cylindrical sintered alloy blocks for piercingtest were repeatedly pierced until the drill is damaged, using ahigh-speed steel drill having a diameter of 1.2 mm, under the followingconditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 38-2.    Machinability was evaluated by the results.

TABLE 38-1 Component ratio of raw powder (mass %) SrCO₃ powder Averageparticle size Co-based Cr-based Fe-based is described in Mo alloy alloyNi C Co alloy Fe Iron-based sintered alloy parenthesis. powder powder#powder# powder powder powder powder# powder Product of the 290  0.5 (1μm) 9.0 10 12 3 0.8 3.3 10 balance present invention Comparative 750.02* (40 μm*) 9.0 10 12 3 0.8 3.3 10 balance products 76  3.5* (0.01μm*) 9.0 10 12 3 0.8 3.3 10 balance Fe-based alloy powder#: Fe-13% Cr-5%Nb-0.8% Si Co-based alloy powder#: Co-30% Mo-10% Cr-3% Si Cr-based alloypowder#: Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C The symbol * meansthe value which is not within the scope of the present invention.

TABLE 38-2 Component ratio of iron-based sintered alloy (mass %) Numberof Fe and inevitable piercing Iron-based sintered alloy SrCO₃ C Cr Mo WNi Si Co Nb impurities (times) Remarks Product of the 290 0.47 1 6 12 33 0.5 11.7 1.1 balance 265 — present invention Comparative 75 0.01* 1 612 3 3 0.5 11.7 1.1 balance 18 — products 76 3.47* 1 6 12 3 3 0.5 11.71.1 balance 152 decrease in strength The symbol * means the value whichis not within the scope of the present invention.

As is apparent from the results shown in Table 38-1 and Table 38-2, thenumber of piercing of the cylindrical sintered alloy block for piercingtest made of the sintered alloy 290 of the present invention is largerthan that of the cylindrical sintered alloy block for piercing test madeof the conventional sintered alloy 44 shown in Table 16-1 to Table 16-2and therefore the sintered alloy of the present invention is excellentin machinability. However, the comparative sintered alloy 75 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 76 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 39

As raw powders, a SrCO₃ powder having an average particle size of 1 μm,a Fe-based alloy powder having an average particle size of 80 μm withthe composition of Fe-13% Cr-5% Nb-0.8% Si, a Fe powder having anaverage particle size of 80 μm, a Ni powder having an average particlesize of 3 μm, a Mo powder having an average particle size of 3 μm, aCo-based alloy powder having an average particle size of 80 μm with thecomposition of Co-30% Mo-10% Cr-3% Si, a Cr-based alloy powder having anaverage particle size of 80 μm with the composition of Cr-25% Co-25%W-11.5% Fe-1% Nb-1% Si-1.5% C, a Co powder having an average particlesize of 30 μm and a C powder having an average particle size of 18 μmwere prepared. These raw powders were blended according to theformulation shown in Table 39-1, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in a vacuum atmosphere at 0.1 Pa under theconditions of a temperature of 1150° C. and a retention time of 60minutes and subjected to 18% Cu infiltration to obtain an iron-basedsintered alloy 291 of the present invention and comparative sinteredalloys 77 to 78 shown in Table 39-2.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 291of the present invention and the comparative sintered alloys 77 to 78were produced and these cylindrical sintered alloy blocks for piercingtest were repeatedly pierced until the drill is damaged, using ahigh-speed steel drill having a diameter of 1.2 mm, under the followingconditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 39-2.    Machinability was evaluated by the results.

TABLE 39-1 Component ratio of raw powder (mass %) SrCO₃ powder Averageparticle Co-based Cr-based Fe-based Iron-based sintered size isdescribed Mo alloy alloy Ni C Co alloy Infiltration Fe alloy inparenthesis. powder powder# powder# powder powder powder powder# Cupowder Product of the 291  0.5 (1 μm) 1.5 5.0 19.0 3.0 1.5 4.4 9.0 18balance present invention Comparative 77 0.02* (40 μm*) 1.5 5.0 19.0 3.01.5 4.4 9.0 18 balance products 78  3.5* (0.01 μm*) 1.5 5.0 19.0 3.0 1.54.4 9.0 18 balance Fe-based alloy powder#: Fe-13% Cr-5% Nb-0.8% SiCo-based alloy powder#: Co-30% Mo-10% Cr-3% Si Cr-based alloy powder#:Cr-25% Co-25% W-11.5% Fe-1% Nb-1% Si-1.5% C The symbol * means the valuewhich is not within the scope of the present invention.

TABLE 39-2 Component ratio of iron-based sintered alloy (mass %) Fe andNumber of inevitable piercing Iron-based sintered alloy SrCO₃ C Cr Mo WNi Si Co Nb Cu impurities (times) Remarks Product of the present 2910.49 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 337 — invention Comparativeproducts 77 0.01* 1.8 8 3 4.8 5 0.4 12 1.1 18 balance 31 — 78 3.47* 1.88 3 4.8 5 0.4 12 1.1 18 balance 199 decrease in strength The symbol *means the value which is not within the scope of the present invention.

As is apparent from the results shown in Table 39-1 and Table 39-2, thenumber of piercing of the cylindrical sintered alloy block for piercingtest made of the sintered alloy 291 of the present invention is largerthan that of the cylindrical sintered alloy block for piercing test madeof the conventional sintered alloy 45 shown in Table 17-1 to Table 17-2and therefore the sintered alloy of the present invention is excellentin machinability. However, the comparative sintered alloy 77 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 78 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 40

As raw powders, a SrCO₃ powder having an average particle size of 1 μm,a Fe powder having an average particle size of 80 μm, a Ni powder havingan average particle size of 3 μm, a Mo powder having an average particlesize of 3 μm, a Co powder having an average particle size of 30 μm and aC powder having an average particle size of 18 μm were prepared. Theseraw powders were blended according to the formulation shown in Table40-1, mixed in a double corn mixer and compacted to obtain a greencompact, and then the resulting green compact was sintered in a vacuumatmosphere at 0.1 Pa under the conditions of a temperature of 1150° C.and a retention time of 60 minutes to obtain an iron-based sinteredalloy 292 of the present invention and comparative sintered alloys 79 to80 shown in Table 40-2.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 292of the present invention and the comparative sintered alloys 79 to 80were produced and these cylindrical sintered alloy blocks for piercingtest were repeatedly pierced until the drill is damaged, using ahigh-speed steel drill having a diameter of 1.2 mm, under the followingconditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 40-2.    Machinability was evaluated by the results.

TABLE 40-1 Component ratio of raw powder (mass %) SrCO₃ powder Averageparticle size is described in Mo Iron-based sintered alloy parenthesis.powder Ni powder C powder Co powder Fe powder Product of the presentinvention 292  0.5 (1 μm) 2.0 2.0 1.3 1.0 balance Comparative products79 0.02* (40 μm*) 2.0 2.0 1.3 1.0 balance 80  3.5* (0.01 μm*) 2.0 2.01.3 1.0 balance The symbol * means the value which is not within thescope of the present invention.

TABLE 40-2 Component ratio of iron-based sintered alloy (mass %) Numberof Fe and inevitable piercing Iron-based sintered alloy SrCO₃ C Mo Ni Coimpurities (times) Remarks Product of the present invention 292 0.48 1.32 2 1 balance 278 — Comparative products 79 0.01* 1.3 2 2 1 balance 23 —80 3.45* 1.3 2 2 1 balance 160 decrease in strength The symbol * meansthe value which is not within the scope of the present invention.

As is apparent from the results shown in Table 40-1 and Table 40-2, thenumber of piercing of the cylindrical sintered alloy block for piercingtest made of the sintered alloy 292 of the present invention is largerthan that of the cylindrical sintered alloy block for piercing test madeof the conventional sintered alloy 46 shown in Table 18-1 to Table 18-2and therefore the sintered alloy of the present invention is excellentin machinability. However, the comparative sintered alloy 79 containingSrCO₃ in the content of less than the range defined in the presentinvention is inferior in machinability because of small number ofpiercing, while the comparative sintered alloy 80 containing SrCO₃ inthe content of more than the range defined in the present invention isexcellent in machinability because of large number of piercing, butshows drastically decreased deflection strength, and therefore it is notpreferred.

EXAMPLE 41

As raw powders, a SrCO₃ powder having an average particle size of 1 μmand a SUS316 (Fe-17% Cr-12% Ni-2.5% Mo) powder having an averageparticle size of 80 μm were prepared. These raw powders were blendedaccording to the formulation shown in Table 41, mixed in a double cornmixer and compacted to obtain a green compact, and then the resultinggreen compact was sintered in a vacuum atmosphere at 0.1 Pa under theconditions of a temperature of 1200° C. and a retention time of 60minutes to obtain an iron-based sintered alloy 293 of the presentinvention and comparative sintered alloys 81 to 82.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 293of the present invention and the comparative sintered alloys 81 to 82were produced and these cylindrical sintered alloy blocks for piercingtest were repeatedly pierced until the drill is damaged, using ahigh-speed steel drill having a diameter of 1.2 mm, under the followingconditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 41.    Machinability was evaluated by the results.

TABLE 41 Component ratio of raw powder Component ratio of iron-based(mass %) sintered alloy (mass %) SUS316 (Fe-17% Fe SrCO₃ powder Cr-12%and Number of Iron-based sintered Average particle size is Ni-2.5% Mo)inevitable piercing alloy described in parenthesis. powder SrCO₃ Cr NiMo impurities (times) Remarks Product of the 293  0.5 (1 μm) balance0.46 17.1 12.3 2.2 balance 182 — present invention Comparative 81 0.02*(40 μm*) balance 0.01* 17.1 12.3 2.2 balance 8 — products 82  3.5* (0.01μm*) balance 3.45* 17.1 12.3 2.2 balance 111 decrease in strength Thesymbol * means the value which is not within the scope of the presentinvention.

As is apparent from the results shown in Table 41, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 293 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 47 shown in 19 and therefore the sinteredalloy of the present invention is excellent in machinability. However,the comparative sintered alloy 81 containing SrCO₃ in the content ofless than the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 82 containing SrCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 42

As raw powders, a SrCO₃ powder having an average particle size of 1 μmand a SUS430 (Fe-17% Cr) powder having an average particle size of 80 μmwere prepared. These raw powders were blended according to theformulation shown in Table 42, mixed in a double corn mixer andcompacted to obtain a green compact, and then the resulting greencompact was sintered in a vacuum atmosphere at 0.1 Pa under theconditions of a temperature of 1200° C. and a retention time of 60minutes to obtain an iron-based sintered alloy 294 of the presentinvention and comparative sintered alloys 83 to 84.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 294of the present invention and the comparative sintered alloys 83 to 84were produced and these cylindrical sintered alloy blocks for piercingtest were repeatedly pierced until the drill is damaged, using ahigh-speed steel drill having a diameter of 1.2 mm, under the followingconditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 42.    Machinability was evaluated by the results.

TABLE 42 Component ratio of raw powder (mass %) Component ratio ofiron-based SrCO₃ powder SUS430 sintered alloy (mass %) Number of Averageparticle size is (Fe-17% Cr) Fe and inevitable piercing Iron-basedsintered alloy described in parenthesis. powder SrCO₃ Cr impurities(times) Remarks Product of the present 294  0.5 (1 μm) balance 0.49 16.7balance 201 — invention Comparative products 83 0.02* (40 μm*) balance0.01* 16.7 balance 26 — 84  3.5* (0.01 μm*) balance 3.47* 16.7 balance141 decrease in strength The symbol * means the value which is notwithin the scope of the present invention.

As is apparent from the results shown in Table 42, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 294 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 48 shown in 20 and therefore the sinteredalloy of the present invention is excellent in machinability. However,the comparative sintered alloy 83 containing SrCO₃ in the content ofless than the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 84 containing SrCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 43

As raw powders, a SrCO₃ powder having an average particle size of 1 μm,a C powder having an average particle size of 18 μm and a SUS410 (Fe-13%Cr) powder having an average particle size of 80 μm were prepared. Theseraw powders were blended according to the formulation shown in Table 43,mixed in a double corn mixer and compacted to obtain a green compact,and then the resulting green compact was sintered in a vacuum atmosphereat 0.1 Pa under the conditions of a temperature of 1200° C. and aretention time of 60 minutes to obtain an iron-based sintered alloy 295of the present invention and comparative sintered alloys 85 to 86.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 295of the present invention and the comparative sintered alloys 85 to 86were produced and these cylindrical sintered alloy blocks for piercingtest were repeatedly pierced until the drill is damaged, using ahigh-speed steel drill having a diameter of 1.2 mm, under the followingconditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 43.    Machinability was evaluated by the results.

TABLE 43 Component ratio of iron-based Component ratio of raw powder(mass %) sintered alloy (mass %) SrCO₃ powder SUS410 Fe and Number ofIron-based sintered Average particle size is C (Fe-13% Cr) inevitablepiercing alloy described in parenthesis. powder powder SrCO₃ Cr Cimpurities (times) Remarks Product of the 295  0.5 (1 μm) 0.15 balance0.49 12.8 0.1 balance 147 — present invention Comparative 85 0.02* (40μm*) 0.15 balance 0.01* 12.8 0.1 balance 7 — products 86  3.5* (0.01μm*) 0.15 balance 3.47* 12.8 0.1 balance 106 decrease in strength Thesymbol * means the value which is not within the scope of the presentinvention.

As is apparent from the results shown in Table 43, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 295 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 49 shown in 21 and therefore the sinteredalloy of the present invention is excellent in machinability. However,the comparative sintered alloy 85 containing SrCO₃ in the content ofless than the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 86 containing SrCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

EXAMPLE 44

As raw powders, a SrCO₃ powder having an average particle size of 1 μmand a SUS630 (Fe-17% Cr-4% Ni-4% Cu-0.3% Nb) powder having an averageparticle size of 80 μm were prepared. These raw powders were blendedaccording to the formulation shown in Table 44, mixed in a double cornmixer and compacted to obtain a green compact, and then the resultinggreen compact was sintered in a vacuum atmosphere at 0.1 Pa under theconditions of a temperature of 1200° C. and a retention time of 60minutes to obtain an iron-based sintered alloy 296 of the presentinvention and comparative sintered alloys 87 to 88.

Cylindrical sintered alloy blocks for piercing test each having adiameter of 30 mm and a height of 10 mm, made of the sintered alloy 296of the present invention and the comparative sintered alloys 87 to 88were produced and these cylindrical sintered alloy blocks for piercingtest were repeatedly pierced until the drill is damaged, using ahigh-speed steel drill having a diameter of 1.2 mm, under the followingconditions:

-   Rotating speed: 5000 rpm-   Feed speed: 0.006 mm/rev.-   Cutting oil: none (dry).    The number of piercing (maximum number of piercing, lifetime) of one    new drill was measured. The results are shown in Table 44.    Machinability was evaluated by the results.

TABLE 44 Component ratio Component ratio of raw powder of iron-basedsintered alloy (mass %) (mass %) SrCO₃ powder Fe Average particle andNumber of size is described #SUS630 inevitable piercing Iron-basedsintered alloy in parenthesis. powder SrCO₃ Cr Ni Cu Nb impurities(times) Remarks Product of the 296  0.5 (1 μm) balance 0.45 16.8 4.1 40.3 balance 143 — present invention Comparative 87 0.02* (40 μm*)balance 0.01* 16.8 4.1 4 0.3 balance 13 — products 88  3.5* (0.01 μm*)balance 3.43* 16.8 4.1 4 0.3 balance 108 decrease in strength #SUS630(Fe-17% Cr-4% Ni-4% Cu-0.3% Nb) The symbol * means the value which isnot within the scope of the present invention.

As is apparent from the results shown in Table 44, the number ofpiercing of the cylindrical sintered alloy block for piercing test madeof the sintered alloy 296 of the present invention is larger than thatof the cylindrical sintered alloy block for piercing test made of theconventional sintered alloy 50 shown in 22 and therefore the sinteredalloy of the present invention is excellent in machinability. However,the comparative sintered alloy 87 containing SrCO₃ in the content ofless than the range defined in the present invention is inferior inmachinability because of small number of piercing, while the comparativesintered alloy 88 containing SrCO₃ in the content of more than the rangedefined in the present invention is excellent in machinability becauseof large number of piercing, but shows drastically decreased deflectionstrength, and therefore it is not preferred.

INDUSTRIAL APPLICABILITY

The iron-based sintered alloy containing a machinability improvingcomponent comprising CaCO₃ and the iron-based sintered alloy containinga machinability improving component comprising SrCO₃ according to thepresent invention are excellent in machinability. Therefore, in variouselectric and machine components made of the iron-based sintered alloysof the present invention, the cost of machining such as piercing,cutting or grinding can be reduced. Thus, the present invention cancontribute largely toward the development of mechanical industry byproviding various machine components, which require dimensionalaccuracy, at low cost.

1. An iron-based sintered alloy having excellent machinability, consisting of 0.05 to 3% by mass of calcium carbonate, 15 to 27% by mass of Cr and 3 to 29% by mass of Ni, the balance being Fe and inevitable impurities.
 2. An iron-based sintered alloy having excellent machinability, consisting of 0.05 to 3% by mass of calcium carbonate, 14 to 19% by mass of Cr and 2 to 8% by mass of Ni, the balance being Fe and inevitable impurities.
 3. The iron-based sintered alloy having excellent machinability according to claim 1, wherein the calcium carbonate is dispersed at grain boundaries in a in a matrix of the iron-based sintered alloy.
 4. A method for preparing the iron-based sintered alloy having excellent machinability according to claim 1, comprising the steps of: compacting a raw powder mixture containing metal powders of Fe, Cr and Ni, and 0.05 to 3% by mass of a calcium carbonate powder to obtain a green compact, the calcium carbonate powder having an average particle size of 0.1 to 30 μm as a raw powder; and sintering the resulting green compact in a nonoxidizing gas atmosphere.
 5. The iron-based sintered alloy having excellent machinability according to claim 2, wherein the calcium carbonate is dispersed at grain boundaries in a matrix of the iron-based sintered alloy.
 6. A method for preparing the iron-based sintered alloy having excellent machinability according to claim 2, comprising the steps of: a raw powder mixture containing metal powders of Fe, Cr and Ni, and 0.05 to 3% by mass of a calcium carbonate powder to obtain a green compact, the calcium carbonate powder having an average particle size of 0.1 to 30 μm as a raw powder; and sintering the resulting green compact in a nonoxidizing gas atmosphere. 